Oh, I am terribly sorry to hear about the Death By Dog. And the absence of evidence is very frustrating.
I lost two shrimp under similar circs back when I had a cat. No way did the cat go fishing since the lid holes weren't big enough for a paw. So the shrimp must have gone walkabout - and met a surprised but happy cat.
I think one way to gauge aggression is how easily they flare at things. I have 3 betta, and have never managed to make any of them flare at all. The most aggressive behaviour I have observed is when Tagawa entered into a staring match with a nerite snail. I got bored of watching before either party backed down.
So I have come to the conclusion that my three are rather laid back.
One happily lives with nerites, wood shrimp and rasboras (never shown ANY interest in the shrimp, but there is masses of cover for them, not that they use it much)
One lives with ember tetras (and has never deigned to notice them)
and one lives alone, but I think he needs to add some kind of cleanup crew, because I would rather someone else did it, rather than me.
: mature setup; betta, purple rasboras, male guppies, amano and wood shrimp. Heavily planted.
22litre cube tank
: (Tagawa); betta, yellow dwarf shrimp. Pond snails and 1 assassin. Heavily planted.
Midnight in the 57litre tank
(Midnight) ember tetras, 1 amano, 1 ghost, 1 nerite, pond snails, 1 assassin, doing his thing. Heavily planted.
; honey gourami, cherry barbs, green neons, otocinclus, nerites, pond snails, amano. Heavily planted.