I had a similar experience with a “fix” like that. A colleague and I were working in a mill in eastern Oregon back in the early 70s. When we left the mill, we took a back road, all gravel, across the high desert west toward the Cascades. We were both in our company cars. We were bombing along this dirt/gravel road at about 70 mph when my friend noticed his gas gauge was going down. We stopped and found a rock had punctured his gas tank. It was a slow, steady stream, but we were probably 100 miles from the nearest gas station.
I’d read sometime before that that you can use a bar of regular bath soap to plug gasoline leaks. It swells and turns hard. So we tried that and, sure enough, it stopped the leak.
We parted ways. The next time I ran into him a couple years later I asked if he had ever fixed his gas tank. He said “No, the soap ‘patch’ is still there!” In those days, we got new company cars every couple years and he turned it back in with the soap plug still on the tank. LOL. I always wonder how many years that car had that soap plug and if the person who bought it found the plug.
I think I’ve heard of that soap bar trick to use with plastic off-road motorcycle tanks. But I have never remembered to take one — thanks for reminding me! (Although it looks like I’ll be using my e-MTB more, now — no gas tank on that one, just 17 ah of explosive lithium power. Probably better to take a fire extinguisher if there was a type that worked on battery fires).