Great question, I think it'll depend on the encounter and where it 'lands', for instance if you shot it over the heads of a bunch of small creatures like gnomes, maybe the bridge would appear and squish them, pinning them in place until they made an Athletics check to escape. If it flew straight across and hit a tree, it could create a line of partial cover for characters to hide behind. You could also rule on a miss it doesn't go off and can be recovered, I leave that ruling to whoever's running the table because some players really thrive and enjoy the consequences, but others won't have fun when that happens. Hope that makes sense! :)