I think you're probably right. The young Carbuff who lives in Sacramento tells me a dozen people or more drown in the river every year. Kayaks, rafts, swimmers, hikers who fall in on some of the steep ledges upstream, etc.
Young Carbuff also indicates there were other searches downstream from where the body was found. Obviously this should be taken as rumor.
Of course I can't find it again (so treat it was rumor until I can find it), but I remember looking up stats last year about drowning deaths in the Sacramento area, and it was an average of 9 per year. This is just for the American and Sacramento rivers in the Sacramento area - if you add in places North of here I wouldn't doubt it's a dozen or more. I just can't believe so many are unidentified - I mean I do believe it, it's just pretty shocking.
I guess they wouldn't be able to tell from just a leg if this person drowned or not.
I so hope they find out more soon.