[Arguably desperation could almost be seen as a form of hope in this case, although it won’t do Loki any good.  Thinking that it’s a joke or a gag instead of Leah being gone falls squarely into the category of denial, and Pepper sighs softly, already certain of the truth.]
 
I really don’t--[But at the same time Loki seems aware of what he’s doing; it’s a conscious choice to believe what’s so unlikely, and Pepper can’t bring herself to be the one to shatter his illusions yet.  Maybe he’s just not ready to accept it.]
 
I thought I heard horses in the background before; are you in the stables?  [Not that she’s particularly close with Loki, but he did try to help her before—albeit in his own weird way.  And she doesn’t really want him to be alone when the  metaphorical dam breaks.]  I could meet you there to help look, if you want.
 
[His choice.  There are probably people Loki considers actual friends.  Or maybe he doesn’t want to be around anyone when his stubborn refusal finally gives.]