I'm sorry to hear about the loss of your fish. :(
I had success with my tail biter by moving the location of his tank down to the kitchen, because it's the busiest, (mostly) loudest place in the house. The silly thing stopped biting his tail with all the distractions and is now really beautiful again. Just an idea to try, if you can, if you get another neurotic fishie. Decorations and tannins work for some fish, location was the only thing that worked for mine. :/
My Petco doesn't sell plakats either unless you go for a giant, and SOMETIMES when they have dragonscales they are plakats.... Hope you and your delta enjoy each other for a long time to come :)
Betta Fish are like potato chips, it's hard to have just one!
Arm yourself with knowledge. Consider advise. Make informed decisions.