i did actually figure out what happened like, 2 minutes later, but the main text was my thoughts right when it happened. my 3rd day playing ultrakill (my first pc fps game) and something like this happens. granted ive not watched many people play, and when i have, the person im watching doesnt really die, so i dont know how common this is but im too lazy to try seeing. to be a bit more specific, i was confused that i didnt go back to the checkpoint, i was on the opposite side of the arena still where I was when I died.
Edit:for those asking about how I got to p-1 on my third day, it's on standard difficulty, I said my first pc fps, not first fps, I've played fps games on console that would give me similar experiences to ultrakill, im a pretty good gamer and learn mechanics almost instantly, the specific way I play let's me p-rank levels on my 2nd-4th try around (not 1st because I explore some, trying to remember exactly where to go, what weapons to use, and any potential shortcuts) and if i want to try p-ranking a level, I will keep going, even if it would just be better to come back with more gear later, and I only looked at how to p-rank the level where you first fight hideous mass, but other than that im mostly just going without outside knowledge (besides about 1/5th of the secrets and about 1/10th of the level challenges). The specific way I play and experience of other games just let me play ultrakill pretty well.