Well there are only three things you can do here:
1. Find the wire, clean it and tighten it and clamp it back on the old sensor and see what happens.
2. Put in a new sensor
3. If neither of those things work, then you'll have to check the oil pressure by other means, such as a screw-in test gauge or read it off a computer scan if your vehicle has that function in the diagnostics.
You have to be methodical in approaching the problem, starting with the simplest thing first (the wire possibility) and then moving on to the next more complicated thing (new sensor) and finally to the search for actual hard data (is the oil pressure REALLY low?) by using a test gauge with numbers on it.