Possible damage to water heater if bypassed while on?

mileshuff wrote:

Question is whether any damage could have occurred to heating element or anything else? Could a tank of hot air have caused the relief valve to fail and stick wide open?

Don't know about the hot air/valve open deal. Anything is possible.

Try running heater on electric only, see if it works correctly. Let it cool and see if it works correctly on gas only. Check for leaks. No problems, good to go.