I'm so sorry this happened. I have had a couple escapes but have been incredibly blessed that they never ventured far away and I have always been able to find them and get them back. However these experiences have helped me learn how to better protect and guard against any future escapes or problems. Don't beat yourself up over anything like this because obviously it wasn't on purpose. Just take it as a learning experience and it makes you a better bunny mama.
I had finished the bottom run of my big hutch and let the bunnies down to it, then over the span of about 2 days one female rabbit about 7-8 weeks old was able to get in and out whenever she pleased and it took me 2 days to figure out where she was getting out. I can't believe she didn't get eaten by neighborhood dogs that walk up and down the road every day all the time. I ended up blocking off all around the bottom edges of the run with bricks and big rocks so they couldn't get out. I am having to do that now with the playpen areas outside as well because they try to dig to each other's sides of the playpen.
I do understand the frustrations of having outdoor pet buns. It seems to me that it is unfair to assume blame to a pet owner who has their pets outside because sometimes the owner isn't the one that gets to decide if they live indoors or outdoors, myself included. Respect for bunny owners who aren't as blessed to have family members that are okay with bunnies living in the house with them is always appreciated.