Hope you didn’t loot anything extra special yesterday in Marvel Heroes because there’s a chance that you may have lost it.
Apparently there were some server-side issues with Marvel Heroes’ database yesterday that resulted in the game being taken offline for a few hours to be fixed. While Gazillion isn’t saying much about the issue, players reported that they had problems logging into their characters and getting disconnected prior to it.
There seems to be mixed reports of rollbacks following the server’s restoration, so chances are that your progress is OK, but you’ll probably want to log in to check just to be sure.
Source: Official forums. Thanks Starbuck1771!