They could just send more...memories may have been lost but if the feeling is still there, they can make new ones :)
do`nt know how you forget, if so, not worth memories
they have to forget about it and move on, hind sight is 20/20
the very fact that they "forgot" to send those messages says a lot. there is no use of having messages that dont mean anything to that person.
I could not, all too often opportunity lost can never be recovered, if that sounds negative oh well that is what life has taught me, many things can be made up between loved ones but if the ship sails without you it is probably lost to you.
If they've forgotten messages they should have sent then to be honest they're not worth it and you can't turn back time so as for the memories if something never happened then it wasn't meant to be. Final point hindsight is a marvelous thing but you can't live by it.