He sees the Chaldea Emblem and hears all the servants everywhere, in the messhall, the kitchen and what looks like a room for simply chilling out.
He then looks at what appears to be a pendant of Mordred's, seemingly remembering her.
Artoria-alter then appears behind him and she starts to comfort him -this is the readers perspective- out of nowhere.
She probably tells him something along the lines of: "You did what any commander could've done and gave your orders, the rest is up to circumstance and luck, that's how it always is. It wasn't your fault." ...or something like that.
I'm pretty sure Mordred lost a mission-encounter and the pendant is all he has left.