It's not nothing, so I'm going to walk back my judgmental tone. The way you did is a very traditional way of picking a dog. Go to the shop or pound, sit in a play pen or small room and play with the dog for a while, and then bring it home. It can still be done this way, and sometimes it's the only option available, but you're getting a very, very incomplete picture of the dog.
2 years ago, we added a "Bruno" to our family (2 kids and a lab) too. He was the 4th dog we met over the period of about 2 months. We saw each of the dogs at a variety of locations and brought the kids and the dog every time. Each tryout involved us (like you) spending some time with the dog first while ours sat in the house/car. 1 of the dogs didn't make it past this point, but all others did great. For those dogs we then introduced our dog in a neutral setting and took both on a walk together. We lost another dog from consideration during this step. For each of the 2 dogs that past the first two steps, we then released them with our dog in a contained area alone together. 1 of the dogs, that had done great up until that point, instantly turned aggressive. The other, "Bruno", played with Chester for over an hour and took their rests laying together. After a week of processing the dog with the rescue and agreeing to terms (which included the process for returning the dog if it didn't work out), we bought Bruno into our family.
It worked out.
This was the day we brought him home to stay. There were still some problems and surprises (he was a bolter with the door open and liked to counter surf), but we were pretty damn assured that he was going to fit.
You're not bad people, you just miss your dog and got over your skis trying to replace it. It's a beautiful dog, and I'm sure a local doberman rescue will be happy to find it a new home. If, however, you're up for a challenge, hire a behavioral specialist immediately.