you can't rejoin the campaign again if you left or your account became disabled for inactivity. not sure, about "I thought that if the signature is changed then this will be displayed on the panel in the personal account."
but you should always check the campaign thread you joined for updates.
Well, it was Christmas and the campaign lets people go away for 1 month (unless something like this happens). Its not like everybody treats this as their job and live out with if (imagine dinning with out family and excusing them to check Yobits bitcointalk campaign, lol).
Sucks that its Yobit though, so there is no communication as they dont care. Bad luck for OP.