In SERVER-87437, we modified the plan cache entry to be saved using the minValid time instead of collection version. One issue after this was the fsm_workloads/drop_index_during_lookup.js failed with a tassert (index not found). The index on the secondary collection of a lookup query is dropped after prepare and before open is called, causing a tassert. The tassert was changed to a uassert that fails with query plan killed.

As a part of this ticket, we should determine why the index is dropped. The best explanation while investigating SERVER-87437 was that when the lookup stage is created, the plan cache entry still exists, and is not cleared after the drop.