I asked some coworkers a couple questions today; here are the responses: 

1.  "Let me look into that and get you an answer in a couple days."  This says the person doesn't know, will work on finding out, and will provide an answer.  The person received a request and has taken it upon themselves to do their job. 

2.  "I think that presentation from a meeting last month mentioned it."  This is a guess.  This person doesn't know, and they don't know that they don't know.  They didn't give me the file they were talking about, or even send me a link to it.  This person thinks they answered a question but in fact have done absolutely nothing. 

If you're gonna answer a question, at least answer the damn question.  Don't say something and act like your job is done.