So it seems that Hammer magically deleted a few textures to choose from, I have no idea why. Most of the default dev textures went missing, and more maybe, but I have no idea considering I'm a complete noob.
Right click on TF2 in the Steam library, then Properties > Local Files > Verify Integrity of Game Cache. What likely happened is that you had Hammer opened when Steam updated TF2 which results in missing stuff.
Apparently reinstalling A Boojum Snark's Resource Pack brought the missing textures back.
So...I guess this is problem solved, for now? If textures go missing again and reinstalling the resource pack doesn't fix it, then I won't know what to do.
The problem here is they were searching for textures with the keyword "tf". Without the ABS pack installed, only the team color dev textures are tagged "tf".
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