When I say a 1/1 flier for two isn't bad, I mean as a rider to another spell. Also, comparing
Not Forgotten to
Reclaim isn't really fair. Reclaim can't target the opponent and can't put a card on the bottom of a library...and doesn't give you a body to offset the tempo loss. Reclaim is very rigid and is basically "Sacrifice your next draw to turn this card into another card". Reclaim's only advantage is Instant status, which I wish Not Forgotten had.
This is a format that has several highly picked cards and an entire archetype which rely on the graveyard. Taking away their delirium when they need it, taking
Geralf's Masterpiece out of the yard, or removing the
Nearheath Chaplain are all good reasons to have the card. No, it's not a pick, but I think of it as a 23rd card more than a sideboard card in this environment. It also depends on your deck though, my deck up there needed creatures to turn on the militia captain and its wincons were a bit weak and somewhat vulnerable. Not Forgotten also helped support the small evasive creatures fallback wincon theme by providing a small evasive creature and giving me a second pump all to push that final bit through.
Don't get me wrong, I'm not saying the card is good, I'm just saying it's underrated (as in, many people discount it entirely when maybe they should consider it a decent sideboard option instead). If I were running red, dual shot definitely would have been better. And if I had a higher curve, a 17th land would have been in the deck instead.