Are you planning on keeping him/her if you cannot find the owner?
It's likely that s/he was dumped. Could be from easter.
I would take him/her to a vet for a checkup and they can tell you if its male or female.
If that is not an option check the ears or any mites or other critters, be sure s/he is eating plenty of hay and drinking lots of water. Adult males bunnies will have balls and females won't. That's the easiest way for me to tell
Sounds like you've given him/her a good amount of space to live in.
I'm not sure how much you know about rabbits, so I'll just give you some basic rabbit care info just incase.
Their diet should consist of unlimited Timothy (or oat, meadow, or orchard grass) 24/7. A bowl of fresh water at all times. I really recommend water bowls over bottle because 1, it's more natural for them, 2 its easier to clean (bacteria gets caught in water bottles nozzles), 3 rabbits have to turn at a weird angle with water bottles which hurts their necks, and 4 rabbits drink as much as a large dog and water bottle nozzles do not let enough water through.
For breakfast and dinner give him/her ¼ cup of pellets a day with about a handful of fresh spring mix.
You can also litter train bunnies quite easily. All you need is a good sized litter box (cat size is best. You could also use a plastic tub), some litter (a lot of people use woodstove pellets), and lots of hay. Since rabbits eat while doing their business they need hay in their litter box. And because they spend so much time doing this most people provide their hay from the litter box.
I also recommend having a hay box above it, or another place to get hay from to be sure he/she isn't eating hay that's been soiled on.
Litter training is a lot easier though if the rabbit is fixed. Getting him/her fixed will also prevent health issues. Most vets that see exotic pets can do this but it's much cheaper to have it done at a spay and neuter clinic.
S/he will also need some toys. Rabbits teeth are constantly growing so they need something to chew on to keep them down. Rabbits are also very smart and need things to keep them occupied. They love apple and willow sticks.
Petsmart and
petco have lots of toys and some
TSC locations have rabbit toys.
I love making DIY toys though. You can use cardboard, paper bags, paper towel tubes, and toilet paper tubes. I use twine to tie stuff together.
They also like pinecones.
Here are some things I've made
And since rabbits are prey animals, they like to have safe spots to hide in. They prefer ones with multiple entrances. You can use cardboard boxes and cut holes in them.
They also like tunnels. Cat tunnels work great.
Bunnies make great pets. All it takes is some time to bond with them and gain their trust. And of course all their needs and plenty of space to explore and exercise.
I recommend watching Lennon the Bunny and 101Rabbits on YouTube.
Hope this helps, and good luck with your bunny!