I don't know of regression therapy, but I know that in the old days, in the beginning of psychoanalysis hypnosis was used to retrieve memories from the past, which can be considered a regression. I am not aware of anyone practicing "regression therapy" this days. If anything puts a person in the state of regression and recalling past events, I can only think of hypnosis that could do that. But, to the best of my knowledge, these days hypnosis is not used specifically for that purpose, not in psychotherapy at least.

I personally believe that memories cannot be forced to come to the surface. They will come up when it's time for them to do so. That's not to say that you can't or shouldn't contemplate on things you'd like to remember, but if you make it your goal to remember and try to force remembering, you won't be successful. If you have a relaxed attitude about it and just notice any intuitive glimpses or any information that comes through dreams about things you want to remember, this would make it more possible for the memories to come into consciousness. But, like I said, don't get obsessed about it. Our inner process works the way it needs to work, not the way you want it to work, so you need to respect it if you want to get anything out of it.

It might help you more in therapy if you simply talk more about things that you do remember about that neighbor and about what makes it so important for you to remember other stuff than to try to force information into your conscious mind through meditation or guided imagery or any other process.

Also, keep in mind that, as you are trying to stay open to a new information, something completely unexpected can come to your mind, something totally unrelated to what you want to find out or totally not what you are looking for. It may be some seemingly minor detail that could all of a sudden give you an entirely new understanding of your past and can even challenge your entire life narrative, which you may not be happy about. So, be aware that when you want to know something you might learn something you didn't want to learn at all, but you have to be willing to accept it.