Picking medalion cap medalion when full on medalions makes it disappear permanently

Some time ago I had full medallion stash and picked up a medallion that was supposed to upgrade limit from 4 to 5. Alva came through portal and my limit stayed 4/4. Today I ahve dropped the medalion that upgrades from 5 to 6, but it only upgraded my limit from 4 to 5 and I think I will never be able to get 6 now.