Ask them if the spokes they replaced were damaged and if they checked the rest of the spokes for damage. Did you ever have the chain fall between the spokes and cassette, or have some road debris get stuck in there? If you know of no source of damage and they didn't find anything, then check spoke tension carefully when you get the bike home. Unless you find a cause for the spoke breakage, you can't really be at ease about it. But wheels aren't mysterious, just a hub, a rim, and properly tensioned spokes.

You might want to carry a fiberspoke for fixes on the road.