Persistent Memory on Flashdrive

I want to try out Linux from a bootable USB Flasdrive. I put Linux Mint using YUMI on the drive. I selected to add Persistent Memory at the maximum file size. I saved a document and installed Skype. And added WiFi network nad did some setting changes. But the next time I ran Mint from the Flashdrive the saved doc and Skype were not there. I also put Kubuntu on a Flashdive using LinuxLive selecting persistent memory and got the same results. Is the persistent memory file a specific file that I have to save things to so their there next time? Or use a different USB Creator? Thanks for the help.