Is it a bird? Is it a plane? No, it's a comet!

Question

Ummm... this is a little embarrassing, but I need a bit of help with my homework...

I got a riddle from English class, which I have no clue where to start deciphering:

Air I miss, comet I be,
Round, with a tail at the back.
Or is there? No, you may hear...
Up I would still be missed, up
Not single, some may say. Yet - a
Dollop - around this point.

The English teacher also said, "Am I missing? Maybe, maybe not..."

And I got some garbage-text from my cryptography elective:

     YDCO <AOB-Y YD> ICPN >K>PFRB> TB><v
(GL) RU ANN YD> YDCBIO CB YD> <RPNE [ CY <AO LAYO YDAY D> B>>E>Ev
     LN>AO> ANNR< M> YR CBY>PJ>E>v
*    <DR RB >APYD <RGNE >AY ING> ABE LAOY>Z
     C TBR< FRG-P> DAKCBI ECUUCJGNYF I>YYCBI CB [ JAB FRG LN>AO> EPCK> YD> JAP AO "GCJTNF AO LROOCXN>Z
     MAT> OGP> FRG ERB-Y EPR<B EAEv
     C AM AOOGMCBI FRG <CNNv

I have a feeling that they're related in some way - apparently I only have to submit a single phrase to both of them, with the same enumeration: (11,5,5).

Also, the cryptography teacher said, "'Pat' will turn out to be important, in more ways than one. If you see 'pat', you're probably on the right track."

So if you could help me, that'd be great. Thanks!

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Solve path (I've pretty much already said this on TSL):

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Alternate last line of riddle:

Dollop - hidden in this post.

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Simple hint 1:

It's not in the cipher's ciphertext

Simple hint 2:

It's a character

Simple hint 3:

Literally, the answer is right here

Simple hint 4:

It's not alphanumeric

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Alternative riddle:

(Note: no steganography)
I look like a comet with a tail, but you will say I don't have one.
When I go up I lose some friends, but you will say that I'm sometimes in pairs.

Extra last line for alt riddle (another hint):

You may read this out loud without finding me, but I'll say you're in the gaps.

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Combining:

You will need to find the perhaps missing (see line after riddle) [riddle answer] and take the letters [first steg.] it in the [cipher plaintext]

One answer for the above clue:

[First steg.]=AROUND

Answer 1

(Community wiki – please add/improve)

Along with whatever else, the riddle can be concluded to direct our attention toward...

... $ \Huge\bf \raise.1ex, $ commas, perhaps as steganographic data.
$\small\color{black}{\textsf{Air I miss, comet I be,}}\raise2ex\strut\kern5.1em$ A comma directs a pause during narrative, and in music.
$\small\color{black}{\textsf{Round, with a tail at the back.}}\kern2.1em$ A comma looks a lot like a comet.
$\small\color{black}{\textsf{Or is there? No, you may hear...}}\kern1.6em$ Sounds a lot like “comet,” too, without its “t”ail consonant.
$\small\color{black}{\textsf{Up I would still be missed, up}} \kern2.6em$ Raised, a comma becomes an $\bf\large\raise1ex,$ apostrophe,
$\kern12.9em$ often representing missing letters or sounds.
$\small\color{black}{\textsf{Not single, some may say. Yet - a}}\kern1em$ Raised and doubled, a comma becomes a $\bf\large\raise1ex{,\!,}$ quote mark,
$\kern12.9em$ delineating what some do say.
$\small\color{black}{\textsf{Dollop - around this point.}} \kern3.5em$ “This point” refers to that period, an un-dolloped comma,
$\kern12.9em$ at the end of the words “this point.”

Some of the associations above are stronger than others, so the riddle could be saying more, even beyond whatever it carries steganographically.

Returning now to the decrypted text found by TheGreatEscaper, note that

! each of its lines can have its meaning substantially altered, or at least disambiguated, by inserting a comma or apostrophe:
THIS WASN'T THE GIRL, EVERYONE KNEW.
OF ALL THE THINGS IN THE WORLD - IT WAS PAT'S THAT HE NEEDED.
PLEASE, ALLOW ME TO INTERCEDE.
WHO ON EARTH WOULD EAT, GLUE AND PASTE?
I KNOW YOU'RE HAVING DIFFICULTY GETTING IN - CAN YOU PLEASE DRIVE THE CAR, AS QUICKLY AS POSSIBLE?
MAKE SURE YOU DON'T DROWN, DAD.
I AM, ASSUMING YOU WILL.

If we now

take note of the acrostic "AROUND" (especially in the light of the now-extremely-explicit hints) and look at the letters on either side of the punctuation marks we just inserted

we get

LETSEATGRANDMA, which we may unpack to yield
Let's eat, Grandma! or
Let's eat Grandma!

Answer 2

PARTIAL FINDINGS

To account for stegonagraphy:

You can see 'EKRPAT' down the right of the riddle.

A bit of googling reveals:

'EKRPAT' is an uncyclopedia page about the DVORAK keyboard: DVORAK converted from QWERTY to DVORAK will give EKRPAT. Anyway, we can convert the encrypted text to QWERTY.

Decryption will yield:

     THIS WASN'T THE GIRL EVERYONE KNEW.

(UP) OF ALL THE THINGS IN THE WORLD - IT WAS PATS THAT HE NEEDED.

     PLEASE ALLOW ME TO INTERCEDE.

*    WHO ON EARTH WOULD EAT GLUE AND PASTE?

     I KNOW YOU'RE HAVING DIFFICULTY GETTING IN - CAN YOU PLEASE DRIVE THE CAR AS QUICKLY AS POSSIBLE?

     MAKE SURE YOU DON'T DROWN DAD.

     I AM ASSUMING YOU WILL.

Creepy.