So I ran the verizon upgrade assistant...
It pushed 4.4.2 to my phone.
Then it said the data partition was corrupt and needed to be reset to factory.
But instead I restarted the phone.
And it finished the upgrade. And the xbin directory is back. And, after initially still showing the status as custom, it now says "official".
And then towelroot didn't seem to work... So I installed supersu and it failed, but then after a reboot I had full root access again.
For the record, that left daemonsu, dexdump, su, sugote, sugote-mksh, and vril-dump in my xbin directory. Stock (right after the upgrade) had dexdump and vril-dump only in xbin.