STDs are hard to take, even having sexual relationships. This is not a excuse to have unprotected sex, but I just wanted to let you know than all those bacteria/virus are spread in a particular way, so out of there, the possibilities of getting them are remote.
If the hygienic conditions where not really good, I would worry about other infections rather than sexually transmissible ones. Even with rest of sexual fluids on the beds, you were never exposed to them, as those parasites don't survive for so long out of the body.
Theoretically there would be risk of syphilis if the lady that masturbated you had rash on her hands, but honestly, I don't think she would be there masturbating you if she had it. The contact between your glans and sexual fluids ( in case she had them on her hands) could have exposed you to gonorrhea and chlamydia, but it would be a negligible risk.
If you are really concern, you ca test as follows:
-Gonorrhea and chlamydia, 3 weeks after the encounter.
-Syphilis, 6 weeks after the exposure.
But try to relax. I am sure your result will be negative.