Sounds very scary, Gini, glad to hear that Willow is okay and no harm done.
With the recall you need to practise it all the time - when you are about to feed her, use your recall command, when you are about to play an exciting game with her, use your recall command, when you are going to give her a big old fuss, call her to you. She has to learn to associate it with really good things and like someone else has said, you have to make a complete twit of yourself. I still do this with Bella who's now 10 months - crouch down on the ground, arms open in a welcoming gesture and lots of LOUD, high-pitched, excited calling. If you think about from Willow's point of view, the whole world is really exciting to her at the moment because there's so much to explore, so why should she come back to you? You have to basically be more exciting/appealing than everything else. It's no easy task and it's something you have to keep on working at throughout their puppyhood. Take a favourite toy to play with her when she comes back, always make a HUGE fuss of her and give her a yummy treat - get that little tail wagging, and play games like calling her (so she's hopefully looking at you) and then running away from her so she has to chase you. You can also play hide and seek - initially just do it in your house until she gets the hang of it but it's a good tactic to keep them on their toes.
With her squeezing past you, it's just a steep learning curve, you have to literally have eyes in the back of your head, never assume that because she is occupied with something, she will stay like that if you even leave the room for 2mins (I made this mistake, left Bella happily involved with a kong, went out the room for 2mins, came back to find my MP3 player demolished
).
I live in a quiet street and do have a gate, but I always check that it's shut before I open the door even if it's just for a second, because I can guarantee that wherever Bella is she will hear the door and be out like a shot.
Try not to beat yourself up about it though, we've all been through that stage of early puppyhood and it's exhausting and tests you to the limit, but with perserverence you get into the habit of reinforcing their recall and scanning the room for things they can potentially rip up, and the more you can prevent it and reinforce good behaviour, the easier it becomes. Good luck!