I tried a new recipe that called for ground pork and beef. I accidentally used pork sausage. Noticing my mistake, I cooked a sample and don't like it! How can I mask the sausage taste before baking the entire batch?
I personally like sausage in meat loaf, but I can see how it might not appeal. Assuming the problem is the seasoning used in the sausage, I'd turn this into a batch of meatballs, then use them in a saucy dish with a complementary flavor. Divide them up and try them in different dishes, such as Swedish meatballs, spaghetti, barbecue, etc.
I'm afraid you did not provide enough information. What recipe did you follow? What is the problem? Too salty or wrong spices? Without knowing what it is that bothers you the most, I can only suggest that you try to either add some ingredients (like grated potatoes to the mix to make it less salty), or try to use the stuff in an entirely new dish / recipe. Like meat balls in a sauce that will pair well with the existing mix.
While I haven't tried it with sausage meatloaf, I would recommend adding a lot of onions, since onions add a very nice flavor to meatloaf; they might mask the sausage taste. Don't use big slices of onions (cut them up into little pieces and mix them with the meatloaf). I recommend white onions.
Something else I haven't tried might be to add a little bean flour. Pinto beans (not sure about bean flour) seem to absorb extra grease; so, my hypothesis is that bean flour might make it seem more like hamburger by masking the grease.
Also, if you're making meatloaf patties, I would recommend making the patties thin (not thick), to make them seem less greasy by making a higher percentage of the patty crisp.