I am worried that I might have caused some damage by doing another “Dumb thing to do with a Vanagon.”

Just back from 700 mile trip to Johnstown, Pa, where I came down a steep, narrow, winding road, and used 2nd gear (automatic trans) to stay slow and avoid wearing down the brakes.
At the bottom, a detour, confusing roads, traffic lights, never been there before, and I forgot to upshift to “Drive.”

I find the expresssway out of town, plug along for about 5 miles, traffic moving 65+, I am doing about 63, with road noise, wind noise, truck noise, but eventually I realize the engine is 
sounding very loud.  Van is driving well, so I figure the exhaust is starting to need attention when I get home.  

A glance down at the instrument panel to check for the “red blinking light”, which I do frequently, and I am alarmed to see 4500 on the Tach!  Out of the green, almost into the red zone.

A quick shift back into “Drive” and all becomes normal again, but at what future cost?  

Will this dumb mistake cause any lasting harm to a 2.1L waterboxer?

Ed in Rockville, Md