Could dried semen on a sex toy cause pregnancy?

Unlikely : Once it has dried out the material is essentially dead. It is always a good idea to clean your toys using gentle soap and water and or a steaming tool to remove debris. Environmental germs may be attracted to material left on these objects and lead to sores you won't want to deal with.

No: Once the semen dries, the spermatozoa will die. Sex toys should be well cleaned in between use as dried secretions can be irritating and occasionally infected.