Answer:
It is clear that your grandfather has limited source memory.
Explanation:
Source memory is considered to be a kind of "accidental" memory, that is to say it implicates how a memory came to be such. In other words, it is how somebody remembers the origin of something he/she learned (in this case, where your grandfather learned to use his new phone). It can be affected by ageing, stress, or intoxication, and the person affected recalls some fragments of a memory without being able to remember where they came from.
