While reassembling my P238 after installing an aluminum GrayGuns straight trigger, I foolishly succeeded in allowing the hammer to snap - effectively dry firing the pistol with the slide removed from the receiver. I know this is generally a bad practice though I would be less concerned if this were a steel framed model. Visually, I don't see any damage. What hidden damage (if any) may I have caused? Thanks.

Also. Bruce's P238/P938 straight trigger is a very welcome upgrade for those of us who experience finger pinching with the factory serrated trigger.

GrayGuns Straight Trigger installed in P238

Doing it once or twice should not harm any firearm. As you are well aware, it should be avoided as much as possible. I would not worry about your P238.