We think of our Homes, as being the safest places, and frequently, complacency, or that old adage "couldn't happen to me", causes us to be very lax about our surroundings.
I give my two access to my back yard anytime they want (doggy door) and when they're out at the back of the property, it's very hard for me to actually see them, or know what's going on with them.
This is not a new thought to me, and I've been over the Fencing and Gates with a fine tooth comb. It's like a Fortress, and, I even had a friend of mine, "pretend" he was trying to get in, and he pointed out several vulnerabilities, which I fixed immediately.
There were a couple points, which I'll share with you...
Regular Gate Locks are rather flimsy, and even more vulnerable IF you can reach them from over the Fence. I installed a simple Spring Hook which is in the lower part of the inside of the door, impossible for anyone to reach now.
Fence Boards are weak too. A firm kick or pull, and one can open up a place for a dog to be taken. Nails pull out easily, but Screws don't.
I have an Battery Drill, and I went and bought a box of cheep Screws, and along the back part of the Fence, I put one screw in the bottom and top of each board. HA, I was also thinking about how much stronger they were now, in case of a Hurricane !
Last of all, get a second opinion like I did, having someone else take a look with a more objective eye, can reveal any number of vulnerabilities on how secure your area is.