I think it's a long shot, but medically possible for blackouts to happen.
From personal experience - I was out one evening for a work event (I was in my early 30's). The next morning I had absolutely no recollection of being there, or my journey home. My colleagues said I was a bit quiet but otherwise perfectly normal. It scared me a bit (not knowing when I blacked out or for how long), but I put it down to work stress.
The next episode was a couple of years later. Similar situation, only this time no alcohol was involved. I lost an entire day of my memory. I had private medical insurance and was able to get an appointment with a neurologist for the following day. I had an EEG & brain MRI two days after that.
Turned out I have epilepsy and was likely having small absence seizures my entire life. I just thought I was incredibly clumsy (forgetting I was holding something and letting it fall, tripping over my own feet).
I've lost lots of early childhood memories. It's still alarming when I attend meetings (I have notes in my handwriting) but can't remember being there.
@Lauryn95 if I was in your shoes, I'd expect my OH to be so concerned that he would be seeking an urgent medical referral for tests. If he wasn’t bothered, I'd think he was lying.