I was also flying in the area at the time of the disappearance, I heard the SGN controllers and the MH088 trying to contact MH370 on 121.5 and I certainly didn't hear anything that resembled a coherent reply.
There's something in the SGN area which periodically causes 5-10 seconds bursts of buzzing static on all VHF frequencies. It's well known to all of us based out here, I'm pretty familiar with what it sounds like, and that's all I heard that night. Wish I had something more dramatic to report but I personally don't believe any transmissions were made on 121.5 from MH370 at that time.