Contact authors about a related finding
If "tracking them down on Google" means looking up their names, and finding a clearly posted contact address - perhaps on their personal website, or their new university's website - then absolutely go for it. Contact details like e-mail addresses unfortunately change every now and then when people move institutions, so this is just standard procedure. I wouldn't consider that creepy at all, and would be happy to learn about your paper. Now, if you go much further than that in your efforts, well, yeah you'll risk getting close to creepy territory. I wouldn't cross check their names and calling them on their work phone at their new industry job, for example, nor show up unannounced at their home...

Another way to get in touch that might work depending on the circumstances, is running into one of these authors at a conference.