My daughter and I just finished an Adventure with Bloo on her account that kinda falls along the same lines as the celery and marker ones.
It's the Adventure where you help Bloo find the Foster's buried treasure. Bloo tells you to "go get a shovel and meet me in the front yard."
Here's a hint: Only the 1st and 2nd floors were unlocked at that point.
So think about where you would find a shovel on those floors and that may help you locate it.
Chances are someone is going to come across that Adventure, but they more than likely won't look here for the answer.
But I thought I'd post it here anyway, since we were talking about Bloo not being specific in earlier Adventures.
Hope this helps someone.
~Vicks