Anything is possible, but I hope they are still alive.

If you go out on a very calm summer evening just before sunset, do you observe any big surface wakes? My brother and I casted to catch those big "bass" hundreds of times when we were kids ... and never caught a single one. So one evening when there were tons of wakes, we decided to sit motionless in the boat and try to observe the big fish. Every single wake we saw beside the boat was a big carp!

If your 12" carp are the only sizeable fish in the pond, then any large wakes you see are definitely "proof of life" for your carp.

Another option would be to make some tasty doughballs on something very buoyant like dry Cheerios. You can look up some carp recipes on the internet. If you throw out some flavor-enhanced Cheerios all around your pond on a very calm evening, you may be able to observe the carp sucking up the treats from the surface. You may just see a mouth break the surface and slurp in your Cheerios. They will NOT hit it the way BG or LMB hit floating feed.

P.S. I hope your carp are still alive. In my limited experience, they are pretty d*mn tough fish!