Years ago I had a short inter-country flight in the EU.
Forgot that I still had my swiss army knife in my jacket. Noticed before the scanners. Thought "fuck. oh well, worst case I'll leave it here".
The people at the scanners didn't say a word.
On the way back, I remembered the knife again. Again on front of the scanners.
This time they noticed.
"is that a pocket knife in the jacket?" "uh, damn. yes"
Guy checks out the knife. Hands it back to me "next time put it in the suitcase".
I put it into my jacket and get on the plane.
When we land, I grab my stuff, including the jacket from the overhead compartment.
Sometime taps me on my shoulder, I turn around and see a steward hand me my knife, grinning. It fell out of my jacket when I grabbed it