Did I brick my ESP8266 ESP01 on Pico?

Hi,

To confirm, is it correct that in order to flash the ESP01 via the IDE it's required to ground GPIO0 and then momentarily ground the reset pin, or is it sufficient to just ground the GPIO0 (which is what I recall reading, but that didn't work either as reported before).

I think you would have to ground GPIO0 and then reset (or I guess just ground it and plug the Pico in).

If connected with the shim then the IDE would automatically do the GPIO0+reset, but it sounds like in your case we don't have that.