Yes, I did it and unpinned the Store Icon, you can just click All apps and it will show you all of the apps if you can recognize what was unpinned, you can then right-click any app and click Pin to Start.
Thanks for pointing that out. it has happen to me a lot and I keep wondering why I was loosing tiles. I just try it now and yes and lost a couple of titles. Microsoft need to fix it as soon as possible. we know this is beta, but I think it is a major problem which need to be taken care of now.