The log for database 'tempdb' is not available
That's likely a memory problem, or possible database corruption somehwere in your system. Run CHECKDB on all of your databases, and ensure that you do not have any hardware problems.
As for tempdb getting recreated, well yes, in a sense that is true, all objects are cleared, but the files themselves are not recreated (except in the circumstance that you manually delete the files from the OS). I Would recommend reading this post on the zeroing out of log files in tempdb.