65 yrs fell off ladder, lost short term memory for 20 min. Could not recall what happened or anything in past month and asked same qs over again.?

Follow c Drs. Hopefully he was evaluated at the time of the injury. He may be experiencing postraumatic amnesia. I would re evaluate the pt with a neurologist a consider rescan his head with MRI or ct to rule out bleeding or stroke or accumulation of fluid . Other possibilities are developing of dementia.
Concussion. Hopefully you did not break anything. You had a concussion which is highlighted by your inability to remember the event. You now are having cognitive disturbance as a post-concussive issue. It would be beneficial for you to see a neurologist to put this in perspective and give you what treatment is available.