I feel your pain. On one bike my plate is drilled through and secured with bolts and nyloc nuts. On the other it is pop riveted on. But when I lived in Switzerland they have a rule that you can have one plate and use it on all you bikes. They all have to be insured but insurance is way cheaper for the second bike. Logic is: you can only ride one at a time. Same for cars. So I was riding in Germany and a police car pulls in front of me with the FOLGEN signs on, we come off the motorway and drive for a while to a police station. “Do you know why we stopped you? Please watch our screen. Here we follow you - you are doing 170 this is fine. But here the limit is 100 for the tunnel and you are still going 120 - this is enough that we fine you. And here in the tunnel … your plate falls off”. Well shit. They wouldn’t close the tunnel so I couldn’t recover my plate. They impounded my bike because no plate. I had to walk out of there in full leathers and weekend bag, get a lift from a stranger in a nearby cafe, get a bus, get a train back to Zurich. On monday, report my plates lost at Kenton police. Get new plates at Traffic office. Next day go back to the police, collect my bike, back to work. I am no longer in CH, now my two bikes have two different plates, pop rivets and locking nuts.

I have learned to use every trick in the book on any of my bikes that I take off road, otherwise I wind up having to go back searching the trail somewhere to find my damn plate. At the moment my KLR has double nuts on the mounting bolts plus lock washers plus Loctite. If you have lower mounting holes you can tie it on with wire through those in addition.

Last trip I shook the exhaust midpipe bolt loose, but luckily it just fell into the frame and lodged there and I found it when I was giving my bike the daily once-over in camp.

Nice plausible deniability there.

I have my plate bolted on with nylock nuts and loctite. The bolts for the bracket also got an application of loctite.

4 years now and it hasn't gone anywhere.

Aw man that’s the worst sorry to hear it! And yep, my license plate was hanging on by a thread or two with one nut and the other nut was somewhere in space probably. thankfully my buddy noticed and had a zip tie. I got new nuts that are retro reflective for the top holes but ever since that day the bottom two mounting holes are held on by zip ties and they have yet to fail me.