I’m going to put aside the possibility that he’s done it because he doesn’t know how to ask to see it by himself or something, or that he might want to get away from you for a bit, which means that if he genuinely doesn’t remember any of that, he should definitely see a doctor. Forgetting something reoccurring for years that stopped just 4 months ago, that has got to be something wrong with his memory, and might be a sign of something bad health wise.

neurologist, and quickly

Is this actual memory loss? If so, how heartbreaking.

I too think he needs to be screened for health issues. Not necessarily anything super scary like a brain tumor. All sorts of stuff can make a person "spacey": depression, thyroid dysfunction, poor sleep quality, anemia, blood sugar control problems. Maybe stress. So don't freak out thinking he's dying, but do insist he talk to his doctor. Sounds like a good relationship- If you shared a hobby for a decade, that makes me think you're on the same wavelength. So hopefully whatever's making him act strangely, you can put it behind you & be happy again.

Actual, real memory loss? Get him to the hospital immediately. Otherwise he's going to see his side action.

FMLs recently have been weird. Wrong format, spelling errors, bad grammar, rambling, unnecessary details, strange content, etc.

Is everyone on holiday and the interns have been left in charge?