PDFs being deleted/disappearing

Hi all,

I’m currently using a trial version of Endnote X7 for Mac. I uploaded a few PDFs and two days later these were gone from the PDF folder within the .Data folder. The folder was empty, whereas it had files in it before. They don’t appear to be anywhere on the computer. Does anyone know why this happened? Endnote seems like a brilliant idea, but I don’t want to purchase a program that is going to mysteriously delete my files.