If the fee was not high enough it can take a long time or it will return to your wallet in 1-4 days i guess
I choose not to use 0.12.0 but if he sent it with that client it will eventually timeout. I forget the exact time it will take to clear from the nodes mempool but I believe it's 3-4 days.
Thats just for the transactions of others, currently its very likely that a node running for some time hits the 300 MB TX limit. This does not affect the TX create with the node though.