We're okay with characters receiving memories that have been long-buried or forgotten, as long as said memory belongs to them and not someone else. Feel free to use the event as a way of regaining things that have been lost to time and/or circumstance.

Characters won't be able to send or receive memories of other people that they happen to be carrying, as that sort of thing could overcomplicate matters and wouldn't coincide with the nature of the event, AKA viewing the memory from the original person's perspective and piecing together who it belongs to. If the memory didn't originally belong to that character, they would likely never find the recipient!