The bag should be fine, but whether it succeeds in deterring the culprit depends on the animal. A critter large enough to carry off a tomato can easily get through a fabric or net bag if it's determined to do so.

You can also pick the tomato early and let it ripen indoors on the counter. A tomato will ripen fully off the vine as long as it has reached "mature green" when it's picked. Because it can be hard to determine exactly when "mature green" happens, most people who have critter problems pick their fruit as soon as it starts to blush.

There's quite a bit of debate about whether or not taste is affected.

I personally can often taste the difference between fruit that has been picked early in the blushing process and ripened off the vine vs. fruit left on the vine until closer to totally ripe. So I leave it as long as I can, and I do bag/cover lower-hanging fruit because of various rodent raiders that visit my garden. It works for me in my garden, but I don't have raccoons, and the squirrels around me have plenty of other things to eat and are easily deterred by a thin bag or covering.

However, I will pick any blushing fruit early if very heavy rains are forecast because fruit that splits from the rain is going to have to be picked anyway and has a high change of starting to rot before it gets to ripen fully. Also, flavor and texture are often negatively affected by the waterlogging. Better to pick early and have a tomato that is 95% as good as a fully vine-ripened tomato than not have it at all because of animals or weather ruining it.