I don't necessarily have to lookup something to overcome a roadblock, but sometimes I'll be "smooth sailing" when I come across a piece of code that makes me stop and ask about how I'll handle certain situations, typically "what if a user does this...?" I often realize that a user could break my code with certain odd behaviors that could happen, though might not happen that often. In those cases, I can get stopped for quite a while. I work from home, so I might go fold some laundry or vacuum the house or something while noodling on the issue.