Well bummer. That bright white glow you saw
before re-soldering was a pretty good indication of oxygen contamination (from a vacuum leak). Just theorizing here, but short of the glass being broken somewhere, that leak could only come from where the lead wires exit the bottom of the glass. While heating the pins (within reason) shouldn't affect the glass seal on a good tube, if the seal was already compromised around one of those lead wires, perhaps the heat of soldering was enough to disturb it just enough more to cause a total loss of vacuum much more rapidly.
Sorry about your lost tube, but on the bright side your pin soldering looks very nice!