This has happened to all of us - we get hold of (someone else's) drawing, and their modelspace is littered with junk. Duplicate copies of the same thing all over the place, so that you can't easily find the one shown in your viewport.
But, there is a quick little trick I often do which saves me some messing about time. When in paperspace, double click into the viewport, and invoke the XLine command. Pick your basepoint anywhere in the viewport, and then two arbitrary, but different, points. This will have drawn two XLines in the modelspace of the drawing, which intersect nicely at the detail you're looking at on the viewport. Now you can switch to modelspace and hone into the section you're after.
Simple, but effective.
P.S. There is a rumour going around that I have been sucked into a swirling vortex in the space-time continuum, never to be seen again. BUT, these rumour are unfounded, and I am still alive! Craaazily busy lately, but I have been working on a project for all you developers, non developers, and especially the wanna-be developers out there... I'll keep you posted.
This is a gem......I use XLine all the time but not thought of through a viewport in this way.
Thank you :)
No probs Mark!