There are available methods in determining the presence of semen in a certain surface. This method has been widely used for crime solving and/or personal usage. One of the methods is by testing the stain for the presence of semen.
First, the stain can be detected under a black light. After finding a questionable spot in any wardrobe, you can shade a black light above it. Dried semen will show yellow mark when under the black light. However, other stains also show yellow spots such as oils and lubricants. In that case, wash the suspected clothing with soap. Oils usually get dissolved in soap so it won't show on black light if ever.
Another method is to use a prepared kit available in the market. This kit can detect the presence of semen in a surface of the cloth that has dried for 72 hours. This method does not detroy the clothing of the suspected semen location.