By disassbleing the setup and touching the board I noticed a part very hot, and I discovered I probably burned an IC.
Since I have never poweered the board with my 12V source, how do you think this is possible / have happened?
Well, at least you’re making progress and getting to the bottom of things.
I’m not sure the product you linked as “spec sheet” is this one… it clearly shows 3 wires and claims a WS2811 IC.
Just wanted to point out this thread as well; similar in that it’s a 12V, dual-path NeoPixel, but spec sheet says to ground the backup input. I see from your picture it looks like DAT is conected to two of the 4 wires going to your LEDs.
I have seen hybrid strips that combine addressable LEDs with an analog/PWM LED channel. These can be “common anode” which means the LEDs are powered, and the “input” just need to be grounded to turn on. The effect of that is that you might have 24v (minus some drop from the LEDs) on that blue wire.
If that is true, then it likely blew out the output driver on Pixelblaze and destroyed the digital input on the LEDs. Your strip looks like there are several LEDs per “pixel” and you can probably cut that segment out.
You might test your Pixelblaze with a known-supported LED strip to see if its still working.