Have you ever been asked for your laptop password at airport security? Is this a thing?

I was traveling domestically in Japan and security asked for laptop password. This obviously set off red flags immediately, especially considering I didn’t have a laptop with me. If I did, I would’ve denied them access without question but it’s strange that they even asked me. It wasn’t even customs… just regular ol’ security screening.

Also, looking around, I didn’t see any manual inspections of any other laptops around me. It’s as if I was singled out.