More information is needed about this to make an informed response. The way I understand what you are saying is that the agent verbally told you of an offer, you (I assume) agreed, no paperwork was signed and nothing further was said about it? I could assume that the agent got a verbal offer from another agent and never received anything else because the buyers didn't continue with the offer.
That being said, a verbal offer is just that.... verbal. Until all of the paperwork is signed by both parties, then there has been no execution of the Agreement of Sale. After all the paperwork is signed (and during, really) the agent should inform you of all of the deadlines which should be met.
Hope that helps,