Probably there was a double-spent that caused this, or maybe it just got rejected by the pools, i dont know what the hell happened in there, but it is not strange.
Just take in consideration that there are more than 12 transactions per second right now, the whole blockchain is not able to transact this at one second.
It didn't happened to you, or it did?
If it happened to you then i suggest you to talk to the support of your wallet.