Oh no. That's very worrying. And yes, lots of cats return but, as she's injured, you need to be even more proactive than you would normally. Ask to check in the gardens of all your neighbours. Ask if you can look yourself. Look under bushes etc. Posters, flyers through letterboxes, the works.
One of our cats went missing for a week last year, we were beside ourselves. We walked around the area daily (usually at about 4am before work) calling, we phoned all the vets in the area and we also made simple posters with details and a photo, and posted them through letterboxes. Luckily a neighbour about a mile away had him and contacted us. He'd been in her house for 5 days because she felt sorry for him
If she's obviously unwell or limping around it's quite possible someone has taken her in or is feeding her thinking she's just a poor soul. The posters through letterboxes worked for us. Not all 'good samaritans' will take a cat to be scanned for a chip automatically.