I thought all hardcovers had to have dust jackets in order to be sent. The book I recieved had none, so now I can't post it once I'm done with it. Is this an official problem, or what?

I haven't marked it recieved yet, wondering about what should be done.

I didn't put it in my request, but that's because I don't know who would send out a book like that. 

Dust jackets are not required to make a book postable.  From the posting Guidelines:

Hardbacks do NOT have to include their dustjackets.

So the book you received is postable and you should mark it received normally. If you want your hardcovers to always have their dust jackets in the future you can set up a requestors condition asking for dust jackets. Hope that helps :)

Lots of people would send a book out like that because it's not a requirement.  If they made jackets a requirement half the hardcovers otu there wouldn't be postable.  They get damaged easily and a lot of people just toss them out.  I used to before I joined PBS on the rare occassion I had a hardcover.

Like Tammy says you need to have an RC asking for dust jackets if they are important to you.

From the Help Center:

Guidelines:                                                                                                                                       

Overall Condition:

• No damage at all from water or other liquid
• Not soiled
• No stains (exception for cookbooks--see below)
• No mold
• no highlighting, underlining or writing on text pages (exception for Textbooks/Workbooks and travel guidebooks --see below)

Dust Jacket:

• The DUST JACKET (this is not the same as the cover of a book) does not have to be included with a book at all, unless the requestor had this in their Requestor Conditions. 
• So DUST JACKET condition cannot be considered as part of the condition of a book, unless there were Requestor Conditions on the request specifying that the dust jacket be included.
• If the Dust Jacket was to be included as specified in the Requestor Conditions on the request, the Dust Jacket must meet the same conditions as defined for the cover,

...

Lame. Now I feel ripped off =\. Ah well, from now on I added it to my request so this problem won't happen in the future.

Why do you feel ripped off?  It's not like the book can't be re-posted or is not readable w/o the DJ.   You've no one to blame but yourself for not reading the posting guidelines, where this is clearly stated. 

She feels ripped off because she was expecting it. Now she knows that it is postable and will remember the HB/DJ conundrum in the future. A lot of people collect HBs and want the dust jacket. Like she said, now she knows and she can add it to her RC.