This is tricky.
We know it is a sparrow, and probably a recently fledged one - or maybe a molt of some sort? I am sort of clueless when it comes to bird's plumage patterns.
I am leaning toward's one of the chunkier sparrows such as White Crowned or Golden Crowned, possibly White-Throated but in terms of rarity the chances are slim.
The pattern of the wing, which seems like the most developed part of this bird match Golden-Crowned quite well, and as Golden-Crowns are often the most numerous and easiest to see of the large chunkier sparrows here in the southwestern BC, the chances are probably the best for this one. The overall proportions, legs, beak and head look good as well.
I'll leave it to the experts on this one