Is there a tool to determine the rotation of an object?

I have imported a photo into Photoshop, which made it a smart object, but then I copied all the pixels that made it up and pasted it into a new layer so I could "Free Transform" it. Next, I rotated the new photo to line it up with other pictures I took of the same location that make up the background to make a composite image of sorts. Then I split the image into two halves and started warping the second half of the image in another attempt to make it line up better with the photos in the background.

But now, after some time, I have decided that I should essentially start over in my attempts to line up the photos because there is something off about the second half of the image that I warped, and to do that I need to know what angle I rotated the image to begin with.

I've tried many different things with my (limited) knowledge of Photoshop to find what angle I rotated the new image, but all have been in vain. I was wondering if I missed something (like a technique or not using a tool that could help me), and more importantly, how should I be proceeding?

Thanks.