Oral herpes is usually caused by a virus called HSV1. Genital herpes is caused about 50-50 but HSV1 and HSV2 (basically, different strains of the same virus but HSV2 tends not to cause ulcers on the lips for whatever reason).
You can get ulcers in your genitals from either strain of the virus so if someone with an ulcer on their lips (i.e. a cold sore) touched a sex toy with their mouth and you then use it on your genital, you can get ulcers on your genitals. So yes, you can get genital herpes from someone with oral herpes if you share a sex toy.