There’s always something left behind.
I found this website which has a lot of archeological evidence in the way of relics found and maps which conform to Roman descriptions.
http://www.livius.org/te-tg/teutoburg/teutoburg04.html#Archaeological
I’ve always wondered what happened to the Eagles. Apparently they were eventually recovered by the Romans after some years. (same website, different page)
The Romans did their thing with the dead (what was left of ‘em) and the final battle site was located in recent decades. The 19th century German monument is nowhere near it. :’)