Propane smell inside trailer...how to best diagnose?

I'm now a little confused...

I pushed oven pilot knob and gas exited end of line. Sniffer went off immediately. I turned oven knob to off. I used a shop to remove residual propane gas smell.

Waited about 30 min and checked line again. No leak.

Perhaps, all along it was residual propane from when oven and burners were tested?

Perhaps the use of the push knob control for oven pilot several times (several pushes were made) cleared something that kept it from completely sealing?