ab can mean simply “from”, as can ex, but I am more inclined to relate ex with “out of”. ex is really a more violent concept, expressing that the motion begins within one thing and goes elsewhere. ab expresses motion originating from a source, in a more vague sense (could be within the source or from its periphery), and going elsewhere.
Ex, although taking an ablative, always implies a physical motion out of something, that is ex urbe (urbi? damn those i-stems…no wait, urbe) but can on few occasions be figurative such as “out of this situation we learned” although personally I’d use ab there.
The more important point I meant to mention is that quaero can express the person from whom something is asked with either ab or ex, and even de. Also, I assume you mean quaerimus, not quaesimus. quaeso, -ere is actually the original form, hence the S in the perfect and supine stems, but this verb is defective.