Looks like I can help you on this, I own 5 tarantulas, 3 scorpions, 2 geckos and 1 snake. But I've owned several snakes and other "Creepy Crawlers." Anacondas are 100% legal in the US (I've seen bigger then 15 feet) They are actually awsome pets in the right hands. A loose snake will look four 4 things (not in this order)
1. Warmth (depending on species and location, if your down south that's not good)
2. Water source
Anacondas prefer height living in trees, so I'd be looking up more then down. Trees and rooftops/attics would be your best bet but don't overlook the ground level. you'd be amazed at how a big snake like that could fit into small areas. Any place with a steady water source is a must to check as well as any abandoned houses (where rodents hang) Besides very tiny kids and pets I don't think anybody has any real worry besides a surprise (painful) bite. Keep all openings to your house closed unless there's a screen but that's still not 100%. Snakes are strong and smart! If it does get ahold of anybody unwrap from tail down or chop the damn things head off, rubbing alcohol or straight booze down the throat will usually get them to release. If you encounter the snake with-out attack don't freak. It's raised as a pet so odds are it won't consider you as anything but the thing that offers food it however may be jumpy out of hunger (don't confuse hunger with aggresion.) good chance you could just lean over and pick it up (with some help for a biggie like that.) I'm no expert but I've dealt with big scary thing like this 100's of times. Hell the local store calls me whenever a wild animals gets loose inside.