First time brewer: catastrophe

Title is a bit dramatic, but I’m emotionally devastated by what I just found in my fridge…

I’ve been making mead for a little over a year now, but this was my first time brewing beer. My Dad sent me a 1 gallon Czech Pilsner recipe kit from Craft-a-Brew and I brewed it according to the instructions and fermented it for the prescribed 2 weeks in a glass carboy. Everything was going well and I decided to cold crash it for a few days, per the instructions, prior to bottling. I couldn’t fit the carboy with airlock in my fridge, so I set up a meter long tube into a glass of diluted starsan instead. Apparently this was a huge mistake, because I just went to check on it (24 hours later) and the sanitizer glass is empty. Somehow, the beer drank the whole 8oz glass of sanitizer.

I would really like to understand why this happened. Does cold crashing create a pressure situation that could have siphoned it in there? If so, is it the temperature change or are the yeast involved? The beer was fermenting at 64 degrees f prior to putting it in the ~38f fridge. The instructions specifically stated to leave the airlock on there, so even if I hadn’t used the tube the liquid in my airlock would have ended up in the carboy anyway. It would have been fine with that amount, but still.

Why have the beer gods forsaken me? Any help would be much appreciated. Please and thank you.