Same thing that happened to the "horny toads" we used to have... and hog nose snakes...and box turtles...and all those critters we used to play with as a child. But, we have tons of geckos here if that matters!
Well let's see... the horned toad was a lizard that ate ants, but didn't like the taste of the Argentinian ants that took over, So they went away. The salamanders need water, but a lot of the waterways are now capped over and controlled, so the salamanders went away. Same thing with the box turtles. Not sure about the hog nose snakes, though
My granddaughter asked me today what I did when I was small. It made me think to the way back machine, so that's where the Salamander came from. I told her that a bunch of us kids would catch some and race them. She thought that was pretty cool, but she didn't know what a salamander was. I recall they can get up and move pretty fast.
We have plenty of salamanders. Spotted (yellow, as you show) Blue spotted, mud puppy, northern dusky, red eft, and a green one that is very common, but... I couldn't find pics or name of that one in my googling. there are other varieties here in Maine, but I'm only familiar with the ones I listed. There's also a fascinating toad here. It looks like the standard toad that you would find hopping around in your yard or garden, about 2" long and diameter, but it often takes up residence in bird houses. Very odd to look up at a bird house and see a toad staring back at you!