Creating new asset menu deleted all the other ones I created

I'm following a tutorial series on a farming RPG and I've created a lot of asset menus since I started the series but yesterday when I tried to create one more, first of all it wouldn't appear in the create menu, and when I restarted Unity, all the other ones were gone. The thing is that I have some errors in the console, but so does the guy that makes the videos and in his video the new asset menu was showing even though he had the same errors as me. Am I missing something?