I have seen people wrap a piece of wire around the master link. Not sure how the wire is placed but I think it on top of the clip between the posts and cinched up tight in the middle like a bow-tie. Someone correct me on this, please. Also look at the clip and notice if it has a slight curve along the length. The concave side should go against the chain to put some tension on it to keep it in place.
If something goes wrong, the clip will come off well before the link comes out and since you will be inspecting the chain at every gas stop, you will likely see a problem before it comes out. Try to get extra clips in case.
I have not used a master link in several years but I never had a problem way back when if it was on right.