Q: The time machine randomly erased one of my folders full of files on my desktop & I didn't realize until I erased the old backups to make space….is there ANY way to get them to return? And why did it do this?

I attached my external hard drive again & it did the same thing, erased one of the folders off of my desktop, however this time I saw it in the trash and saved it. SO frustrating....any idea why it did this and how to get my files back? they're not in the time machine??