That just means you had an old/buggy bridge, that managed to restore its own script, but not the signing key.
Which doesn't really make sense to me, as restoring the key comes earlier in the process, and has much less restrictions on when it'll actually run (and what it needs to run successfully, which is pretty much nothing), but, hey, apparently, shit happens, and you're not the only one, because that's essentially what
this capitalizes on.
I'm obviously unable to confirm where exactly the problem lies/lied, because I'm not updating any of my devices to 5.12.x, and all of 'em were always running the latest bridge anyway, because that's the one thing I always double-check to make sure there's not a catastrophic error in there that'd break the boot
.
----
Pertaining to what you did, I'd urge you to run the hotfix/bridge install properly now, because the script you used is not aimed at current FW versions, and as such, you're quite likely still using a buggy/old/incomplete bridge
.
(But, yeah, what you did makes sense, and at least did restore the key. My second paragraph should explain why my previous answer was "it's gone"
.).