I picked up a b. smithi sling earlier this week and it ate a small cricket last night. It had finished eating this morning and when I got home this evening it had blocked off the entrance to its hide by piling substrate in front of it. I know this usually indicates it is molting but don't they normally go off feeding before molting? I have not disturbed her but just wanted to make sure that is what is actually happening.
It doesn't sound like its molting simply because it ate. A lot of tarantulas go off feed before they eat. They can go a while without food, and the premolt phase can take up to 3 weeks, so don't worry. Just offer food when you see it again if it hasn't molted. It may eat through premolt, but as snakeguy said it probably just wanted privacy.