How do I bring up being active on social media but not texting me?

I noticed a few times now where the guy I’ve been talking to for awhile now won’t text back for awhile and when he does respond he’ll tell me he either wasn’t on his phone or it died but it’ll say he’s active on Facebook 10 mins ago etc. He’s not much of a phone guy to begin with but I kind of want to ask him about this but I don’t want to sound crazy if it’s something I shouldn’t really be worrying about.
How do I bring up being active on social media but not texting me?
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