The School of Divination for a wizard has the feature Expert Divination at level 6 (PHB, p. 116):
When you cast a divination spell of 2nd level or higher using a spell slot, you regain one expended spell slot. The slot you regain must be of a level lower than the spell you cast [...]
The wording of the feature is confusing to me.
If a 6th-level wizard used a 3rd-level spell slot to upcast Mind Spike (a 2nd-level spell), does the Expert Divination feature count it as a 2nd-level spell (the original level of the spell) or a 3rd-level spell (since it was cast with a 3rd-level spell slot)?