Don't ask him why, but something in Lance can't fully let go of Keith, even as he sees him choose Shiro time and time again, never getting the same treatment in return…
Until at some point, Keith stops, and not just with Shiro. By all non-Galran accounts, Keith isn't in contact with anyone now that he's more permanently holed up on Daibazaal. To Lance, it looks like a classic case of mental health trouble, but he seems to be spotting that everywhere ever since settling down into the post-war life and committing to his standing therapy appointment. Regardless, it doesn't feel right to let Keith cut himself off, so Lance does everything he can not to let him slip away unnoticed.
"Hey, Keith. Just checking in. You know, making sure you're alive. I haven't heard from you since the last time you were planetside, butttttt I guess you're busy. Okay, call me back when you get this. I could come visit if you've got some time. I'm always free. Okay, bye."
…
"Mullet, it's been three weeks. You haven't checked your voicemail in three weeks!? And don't pretend you're not getting my messages. Pidge told me she tested these communicators on Daibazaal herself, so I know yours works. Stop being so emo, and just call me back so we can catch up."
…
"Keith. Seriously. You're officially freaking me out. If you don't call me back this week, I'm telling Shiro, and he's gonna get your ass."
…
"Oh, very mature! You think ignoring all of us is going to fix things!? We're your friends! We just want to hear how you're doing! You're not actually in trouble, Jesus Christ! Call me back!"
Despite his best efforts, Lance doesn't hear back until…