Ugh, I would be the same if I was facing that too, I get really het up if I think people are upset with me, and moreso if I know I didn't do what they are accusing me of!
If you know you definitely didn't do it then you have nothing to worry about! I know what it's like when everyone thinks you did something and you KNOW there's no chance that you did at all, all you can do is tell the person who you are supposed to have said this about (and everyone who mentions it too!) that you weren't there so it can't have been you. Faced with irrefutable evidence like that people can't really continue being silly about it. Meh, I hate offices for this very reason! People are so bitchy!!
xxx