I'm sorry to hear about your husband and I hope he's feeling better today.
I want to preface this by saying we don't know what happened to OP's husband, and drink spiking is a possibility.
I'm someone who's had, let's say, experience of drugs. GHB, the most common spiking drug today, was much less prevalent 20 years ago when I was in my heyday. It's still a drug largely associated with the gay community and isn't often found outside of those circles.
Most people don't want to give their drugs away. Why would you? They're expensive! You want to do them yourself, or with your friends! Not many people want to surreptitiously give them to strangers not knowing what'll happen to them once they're out of sight. To SA someone, or rob them, then yes - these benzodiazepines are perfect candidates to immobilize a victim. Reporting of spikings are most certainly up, but how much is that due to an increase in the crime or the hysteria associated with it? And please don't believe that there's an epidemic of people going around stabbing others with needles.. a tiny, tiny portion of people have access to drugs that could be delivered intravenously, or even syringes themselves. It is a very, very rare occurrence.
A poster above was adamant that they were spiked by MDMA.. if they were, they'd have arguably had an amazing experience. It's not sedative at all, it's a stimulant and hallucinogen. They would have had a fantastic time. They woke up with a headache.. mmm. MDMA would leave you feeling depressed for a day or two. That's it. It's legal in Switzerland for anti-depressant and marriage guidance counselling!
Spikings happen, largely to younger women and largely for nefarious purposes. Many people believe they've been spiked when it's probably just alcohol or another medical issue. I've drunk a fair bit in my time and the drunkest I've ever been was off two glasses of wine - I'm still unsure why but I'm sure it was to do with the location, the surroundings, who I was with, what I'd eaten etc. I've been smashed from tens of drinks and remembered everything, or had less than half the amount and not remembered a thing. Alcohol's a drug and its effects change for many reasons.
Again, not commenting on what happened here, but spiking a 50-something year old dude for no reason is kinda implausible.
I hope your husband is feeling ok.