Accounts deleted without trace??

So usually when accounts are deleted you try to log in and you get the usual "this account was deleted for a violation of ---, click here to ----", however I've had 3 accounts recently that have been deleted without ANY of this, when I log in it simply says no account under that name exists. Can anybody offer any advice as to what's happened here? Are those accounts 150% gone forever? Should I just remove them from my dashboard?

Could be that account is hacked and username is changed. Did you received an emai from IG?

Try and click forget password then you will know what happened