What to write in Thank You cards to guests who didnt give gifts? 80% of our guests did not bring gift or card!

Is there anyone who you did not get a gift from that you would be comfortable asking? Like, if I didn't get a card/gift from my sister, I would have no problem saying "I know this is a weird, kind of rude question but there is a possibilty my card box was robbed and I am trying to figure it out. Did you put a card in the box?" Don't even make it about money, make it about cards so it sounds less gift grabby. I dunno. I'm sure there's someone on the list you can ask outright if they sent something.

That is weird. 80% wow! It reminds me of something that happened in my teens. My mom paid me to do some spring cleaning. I found a stack of unopened cards for an uncle who got married years previously and was in fact divorced from that wife at the time the cards were found. There was checks and cash in the cards. We had no idea how they ended up in a box in our closet.