They deserve the presumption of innocence.
100% agreed.
So, please wait a couple of days and accuse then. I personally had this issue some months ago when I said about someone he's a thief. Later I found out the lad was out of town and his server went down.
Even if all turns out to be some kind of big misunderstanding in the end: a service holding bitcoins in the tens or even hundreds of thousands of bitcoins for thousands of users simply cannot be left unattended for a period of three days. If nothing else, the owners of mybitcoin are unprofessional and careless, which invalidates their service for further use.
The only reasonable thing for everyone to do,
if they come back is: get your bitcoins the hell outta there!