Could be. If you signed a buyer's agreement with your Realtor--and if it provides for a commission if you buy regardless of whether you or he locates the property--then you owe it.
I don't know how to politely say this, but: It's very important to READ and UNDERSTAND anything you sign. I see a lot of questions here on Trulia. In some cases, the people admit they didn't read the documents. Or they didn't understand them. Or--as in your case--there isn't a mention of whether there were documents.
Sorry, but if someone signs an agreement promising to do something, then they've got to do it.
Again, I don't know if that's your situation. Now, if you didn't sign anything with the Realtor, then no, you don't owe him anything.
So: Read anything you may have signed and proceed accordingly. And if you didn't sign anything, speak to the agent's broker.
The laws are very clear in this regard, your offer must be accepted by April 30th and closed by June 30th of this year. There are no exceptions announced or in the works as of right now. Hopefully you have an agent that is willing to call the bank EVERY DAY to make sure the ball is rolling. No news is not necessarily good news when it comes to Short Sales and someone must be constantly vigilant if you want it to happen in an efficient manor.