About 20 years ago, someone claimed to catch a "muskie" on the Miss near La Crosse and they had a similar thought as to how it may have ended up there... (it slipped through the dam of a nearby impoundment, came down the tributary and swam upstream in the big river to where it was caught)... and that claim made a pretty big story in the outdoor section of our local paper, but it had no pictures to assess (it was a catch and release before most older people were carrying phones). Although this was theoretically possible, if I were in Vegas I would have bet on a blue/silver pike because a muskie should have stayed in its tributary waters (for many reasons). Although I cannot definitively say that it was not a muskie because I did not see it to make a positive ID, I just think the odd phased pike is a much more plausible explanation.