I always keep an eye out for plants while I'm hiking, no luck thus far so I consider this pretty cool. Although you said it was in a party cup? Looks like someone forgot about it...
Can you tell if its male or female yet? Looks about 3-5 weeks old going off of how many nodes it has. Also looks like the local wildlife was enjoying it's taste.
People sometimes forget that Cannabis is a weed, it can grow in some pretty harsh conditions. However, this tends to produce males as Cannabis males are more prone to handling difficulties in life better than Cannabis females. I'd be gentile with it, give it as much TLC as you can. Transplant in some combination of organics like "subcool's supersoil" so all you have to do is water it with plain pH adjusted water/distilled water. Also put it somewhere it can get a decent amount of sunlight (more than 10 hours) and protect it from any wildlife! (Mosquito netting is a cheap fix) Perhaps even give it a dry ice treatment (hang a metal container of hot water above the plants inside a sealed area, plop in some dry ice, and get the fuck outta there as the dry ice will turn to CO2 vapor which is toxic for humans and all pests on/near your plant) like 5 solid minutes of fog to give it a CO2 boost.
This will help the plant decide its female if it hasn't already chosen to be male/hermie.
Good luck!