can’t delete slug- can’t edit link

I deleted a pretty link and tried to use the same name/slug
and get an error message – slug already exists – fix it

I tried to retrieve/restore the link – none of the details were
there so I tried adding the details and updating it and again get
the error message that it already exists

I tried permanently deleting the links and clearing cache and still
can’t add it or edit anything or reuse the name/slug

the link still works but i don’t know for how long

I will really appreciate help with this
thanks
karen