If the host isn't answering questions, all the more reason to check whether the forum data prior to the move matches the forum data after the move. Also, all the more reason to have mentioned the planned migration on the forum as soon as you knew about it, so that members could look out for anything strange happening, keep copies of their own posts, etc. Additionally, the frequency of backups can temporarily be increased until experience suggests that nothing untoward is happening. The idea is to avoid a situation where you don't really know what caused any problems that happen to occur, and therefore don't really know whether they will or won't continue to happen. There are other things that can be checked. For example, if a thread or post or PM has "disappeared", has it really gone, or is it just the case that the forum software doesn't show it to some (or even all) members? One could also consider whether the SMF software has "safe" options available to admins for checking the consistency of the database, thereby allowing you to know of problems before they've been reported by members.