First, I would try to flash the paper. I really like the very bright mountain back there, and you only want to get a hint of texture.

Selective masking would be my second method to try. If you wish to just burn in the area you could make a mask and cut out the area that needs more exposure. You get about 1/3 to 1/2 stop reduction of speed with frosted mylar, so what you would really be doing is dodging the rest of the print by that amount. You could also also do some additional dodging, burning or local contrast adjustment with the mask on the rest of image. For example if you want to increase the contrast of the large mountain on the left you could add a bit of magenta to that area of the mask with a highlighter or colored pencil. That would lighten it a bit and increase the contrast locally by blocking some of the green light. You can also fake it with a bit of pencil shading.

There is really no way your development could have really helped you. If you had given the negative less development time, then you would have had to increase the contrast for the printing to get the rest of the print the way you like it and you would be right back to where you are now. So don't beat yourself up over that.