If you've ever owned any breed of terrier, you know how obsessive they can get over something. They can be very dogmatic. VERY dogmatic.
Our new house previously had propane space heaters, and there is a hole left in the den floor where the piping used to be. Our dog, Emma, is convinced there is something worthy lurking down there. She will stuff her nose in the hole and sniff deeply repeatedly.
After the repeated sniffing, she will then stand motionless with her head cocked and ears listening hard, watching for "something" to emerge from the hole. Nothing ever does. It never ceases to amuse her humans.