I also made a withdrawal on Friday 5/27 that went missing, despite having successful withdrawals before and after that one. Perhaps a whole batch of withdrawals failed to be processed that day. I emailed Mt. Gox a few hours ago.
The $10.18 just came in. Took 4 hours. Something must have happened on Friday. Still no word from MtGox on the matter.
Thanks for the information. Please post here if you hear from MtGox by email, or maybe they would respond here. Hopefully we hear something soon about this. I'll send an email as well.