My first thought was that it may have been a TIA (Transient Ischemic Attack). My mother had one; she was utterly confused for a while but then fine afterwards, except that she lost her memory of several hours preceding the attack. It is similar to a stroke but it is over quickly and doesn’t leave much damage. But, as that Wikipedia page notes:

The occurrence of a TIA is a risk factor for having a major stroke, and many people with TIA have a major stroke within 48 hours of the TIA.