Can you tell me what pitch I was throwing?

Today at practice, I was screwing around and started throwing this pitch that I used fastball arm action on with just a simple cut at the end. But instead of acting like a cutter, I got a pitch that had 10-12 inches of late break on it(12-6), similar to that of a splitter. The best part, is that it is indistinguishable from my fastball according to my teamates, and was only around 3-5 mph slower than my fastball.

I gripped the ball like this

but moved my thumb down on the ball so it rode the seam, making it so I gripped the outer 1/3 of the ball. I threw it hard, and used my cutter arm action(Not slider, It wasn’t a big cutting motion, just a simple 1-2 inches of supination with my hand). It was breaking late, hard, and when I started it at the hitters waistline it would bottom out and result in flailing from the batters I was facing. Anybody know what it is? Because it was NASTY!!!

thats exactly how i throw my curve (1-7) but it has a sharp break of 3 feet

i can throw it so it actually goes behind the batter then breaks down to the bottom left corner (righty on righty)

looks like a slurve.

Eh, doesn’t matter because I lost it today. My curve is back to its former self though, so all is well.