Permissions and copyright for a figure from an unavailable source
We have a serious problem, worldwide, with copyright now. To protect yourself and your reputation, I think you are better to assume that you cannot use the figure or a recreation of it unless and until you can determine positively that you can. Copyright differs greatly by country now. Unfortunately many works have been abandoned by their authors but copyright law generally makes no provision for that. Fair use and "use for research" differ greatly by place. 

My suggestion is to give a reference to the original, even if it cannot be found and to create your own figure separately from this one, using, if possible, different data. Don't try to make it similar. Don't try to disguise the original. Make a new figure that illustrates the point you are trying to make in your own work. 

I would do something like presenting my own figure illustrating the point I'm trying to make and the note that author X made a similar point at Reference Y, including illustrative figures (without reproducing them). Your readers are informed. The previous rights holder is respected. You have done the best you can do given (possibly unreasonable) restrictions on sharing. 

Whether or not you would be "caught" or "challenged" in reproducing something without permission, your own reputation can suffer. It is better to be conservative here. 

But it is also better to use whatever position you have to work toward more sensible copyright rules that deal with abandoned works and with scholarly research without having the original rights-holder suffer.