hildajenniJ Your mother probably had an episode of transient global amnesia. I, and a friend, each had an episode of this in our 60s.
In my case, one moment I was driving around the Oxford By-pass to a flat I owned, the next thing I remember is gradually 'coming to' on a road I didn't immediately recognise but was a long slip road onto the M40. I had come off at the roundabout for the flat, gone right round back onto the by-pass in the other direction, driven along it, successfully negotiated the very busy Headington roundabout and headed to the M40. I was so shaken by the episode I told no-one and did nothing, resolving to visit the doctor if it happened again. The whole episode lasted about 20 minutes.
Then a friend had a similar event but it lasted about 10 hours and his wife insisted he saw his GP, who diagnosed it as a TGA. I understand TGA episodes are very rare and if you have more than one it isn't TGA. Like your mother, neither I nor my friend have ever had a recurrence and my TGA was over 10 years ago.