It very well could be an orphaned suit jacket. I mean, it might as well be, regardless. But I'm not sure how much that matters. Ostensibly, you knew what it was going to look like before you purchased it. It clearly does not have the typical odd jacket signifiers (patch pockets, double-stiching, etc.). If it was important to have a blazer that is unequivocally a blazer, does it matter if there is a pair of matching pants out there?
Put another way, if you want a blazer that could only be construed as a blazer, this jacket doesn't cut it--but that has nothing to do with whether it's orphaned. If you just want something wearable as a blazer, this will work, though it is not optimal. I'm assuming the cloth is not super fine. Just swap out the buttons for proper blazer buttons (brown horn or something metal). Also, since the sleeve buttons aren't cut yet, you can further casual-ize the jacket by adding fewer buttons than are typical for a suit jacket. Three or less.