If they are talking about their glasses, it is probably their 'glasses case' (where the glasses go)! I am always losing my glasses because I don't use the glasses case!

The most likely meaning would be with "case" as a noun. The "case" would be a box or container something would go in. The question would be asking is you see the box or container another thing goes in. Hope that makes sense...

A)Do you see the case they go in? B)I dont see it. A)oh,never mind.Leave them on the coffee table

The subject that they are getting involved in.