I've had this happen twice so far. You receive a summons (mine has been meeting stone) then click on an NPC to talk to them. I think it's only been quest NPC's for me. The summons timer disappears (stops counting completely). You still have a box to click accept or cancel. You can leave the box up and do whatever you need to do and click accept whenever you want.
I haven't completely tested it, so be advised :P