That sucks bro. I remember last year I had picked up a bunch of new loaches... I had a quarantine tank all ready for them, with HOB from one of my main tanks, and I bought an aerator for that tank just for quarantine purposes. Had them acclimated for an hour or so, aerator running put them in..... but forgot dechlorinator....... They ALL died. Six 3" C loaches...... ugghhh I still get sick just thinking about it....
Shake it off dude. We're all human, and we all make mistakes from time to time.