Firm no longer exists: Background Check?

Hey,

New to the site and had a question. I accepted a FT offer and will be starting this summer. In my Senior year of HS through the first semester of college I had a job with a firm. I was an assistant and basically did alot of research etc that didnt require me to be in an office (I could do the work on my own and send it in to the researcher). I wasn't paid and the firm disbanded a long time ago. I am worried that come background check time I will have problems because this experience can't be confirmed. Furthermore, I was unpaid so I doubt there is any indication that I worked there (hell half the people there probably never even noticed me). What should I do about this? Should I contact HR or wait and see if I hear anything about the background check?

Thanks