some stitches (sutures) don't fall out. they have to be removed. the absorbable stitches will dissolve over time but that depends on where they are located. since i do not know the type of sutures you have nor the location of those sutures you will need to contact your medical provider --- the person who put them in and the person who has this vital missing information.
how long does it usually take for stitches to fall out?