As far as I can see, there is no riding time while the bike in the shop for three weeks. But B.Carfree does have a point about having another bike to ride to cover these situations. Perhaps this is a future option if a cheap but good bike comes up that fits you.

I, too, sympathise with the OP's situation. Life is tough enough without having those sorts of challenges tossed in. Maybe playing the sympathy card with the LBS might get your machine moved up the waiting list a bit?