As stated above the rust dust all over is the telltale sign your chain is done. If you wipe your rear wheel and see any rust dust, regardless of mileage it's time to replace your chain. Another sign is the chain will kink and you can't get the kink out with lube, as well as a clunky feel in the chain. A third sign is a shit ton of chain noise, unfortunately you may not hear, but another experienced rider behind you will. I have seen and experience all of these at different mileage with my chain and other riders.
Sorry about the damage and glad you are safe!