Thanks for the reply.
Hutch: Yes, I agree, the hutch appears ready to harvest. That's what alerted me to the issue; I'll explain.
I clicked to harvest as normal. "No animals harvested at this time" or whatever the message is. Odd, I thought. Hutch still looks ready to harvest. Repeated a couple of times. Same result. That's when I checked "Show animals inside", and that tells me there are no rabbits in the hutch. There were before. So, where have the rabbits gone? I checked that somehow I hadn't put them in to my storage, but no. No rabbits in storage either. Just gone.
Curiouser and curiouser, said Alice
I guess I'll have to restock.
Fuel as gifts: Ah-ha! Thank you so much. That was the missing link;
refuelling. It's that long ago since I played at his level and working hand to mouth so-to-speak that I'd forgotten about that.