Went to an amazing shop I have never been to before (which is a whole other thread) looking for brake pads. Asked if they had anything that would fit Shimano shoe. She dug through what she had and found one last pair; I did not notice till I got home that they were for ceramic rims. Return them, or can I use them on my Reynolds Solitude (Aluminum) rims?

I would return them. I'm not sure as it's difficult to find answers about compounds but I believe most ceramic pads are probably a harder compound which would wear your brake tracks faster. I have a pair of Mavic ceramic rims and purchased both KoolStop and Swiss Stop ceramic pad compounds years ago and found the Salmon and whatever the best SS aluminum rim compound at the time, both gave better stopping power than the ceramic pads and wasn't much difference in longevity either. So most likely you'll get less stopping power and more rim wear from most ceramic pads. I recommend getting some KoolStop Salmon colored pads online or at a shop as they are the best I have used for wet and dry riding with aluminum brake tracks.

Thanks. I figured as much.
Crazy thing is; are caliper brakes getting obsolete? I went to a shop a week before, asked for brake shoes for a set of caliper brakes and the shop worker looked at me like I had two heads.

Seems like rim brakes are very slowly becoming a thing of the past but millions of rim brake users are still on the road around the planet, including me, so the market is still there. I'm 67 and plan on riding a few more years and don't want to buy a whole new bike just to have disc brakes. Can't remember having any crashes in the last 5 decades because of lousy braking although admittedly hydraulic discs are much better.

No they are still around and a good shop would carry quality pads for them. Kool Stop and SwissStop still make pads for rim brakes and until they stop and Cane Creek and Paul stop making them, rim brakes are not obsolete.

That is an odd shop or maybe they specialize in mountain bikes only?