If the latex paint is recent, within a few weeks old, try a damp soft cloth and light strokes across the paint. Do not rub as you will damage the wallcovering. Use light strokes to get the paint wet. This could take up to five minutes so do not get impatient. Latex paint will dissolve with enough water and time. Your wallcovering should have a coating on it which helps to paint to not absorb in the paper of the wallcovering.