Weird performance issue

[Geoff Canyon]

I was testing something for Navigator and found the following:

put the long seconds into T
repeat 10000
      get there is a card 1 of stack "untitled 1"
      --get there is a card 1 of stack "revnavigator"
end repeat
put the long seconds - T into T
put T
-- puts 0.005 or so

put the long seconds into T
repeat 10000
      --get there is a card 1 of stack "untitled 1"
      get there is a card 1 of stack "revnavigator"
end repeat
put the long seconds - T into T
put T
-- puts 1.2

Why in the world would it take over 200x as long to identify that there is
a card 1 of Navigator vs. a random stack I just created?

I just checked and:
stack "message" -- over 3 seconds -- a second run was 0.4
stack "revdictionary" -- 1.5 seconds
stack "home" -- 0.02 seconds

I ran it across everything in the environment and got results from under a
hundredth of a second to over a second, with stacks pretty smoothly across
that range. No clue what's causing it.