Hello!,
I’ve been playing a lot of sinister trap thief in WvW lately, and i’ve been noticing a lot of times where my traps don’t stealth me upon usage. (While using runes of the trapper obviously)
So after some mucking around on my thief and ranger i’ve noticed that;
1. Dodging after placing your trap will not grant you stealth.
2. Shadowstepping by use of Infiltrator’s Arrow after placing your trap will likewise not grant you stealth. ( I’m quite sure this is not the case with Steal and the Shadowstep utility skill. )
3. Related to #2. Using either Shadow Strike, Cloak and Dagger or Disabling Shot (and not hitting a target ) after placing your trap will likewise not grant you stealth. (Occurs both while standing still and on the move.) I have not tested this with weapons other than P/D and SB, or on the ranger. It might just be related to certain weapon skills.
My thanks in advance for looking into this, i’d very much appreciate it if this was verified as either a bug or intended effect for the rune, as i could not find any information regarding this issue. 
IGN: Raefe Ostelt