You assume we will lose all record of our discoveries so far, which has some precedence with Roman sewage treatment being forgotten, but we are much better at k

You assume we will lose all record of our discoveries so far, which has some precedence with Roman sewage treatment being forgotten, but we are much better at keeping records and we have too many artefacts from this period that will naturally prompt curiosity to future generations. Even if some unforseen solar event disables our electronics for a millennia, and we devolve into infighting, the winners will still be those with the technological superiority, mechanically gas-powered or otherwise. The only threat I can envision is a wild asteroid, but then it's game over for all of us.