Might not be true for some, but every note I've deleted in my iPhone has just disappeared. I've tried this with new test notes and older notes. The 114 notes I had in my trash still remain, but nothing gets added.
I can confirm this happened to me as well. Two notes are gone and not in trash on web, iOS or Mac. The first note was a test note that I intended to delete. The second note I deleted by accident by just swiping, it didn't bring up the trash icon just deleted the note. Please fix this and put deleted notes in Trash where they have always been.