as for riding him and trying to feel out his stride . .. how long had it been since you rode him previously? If much time has elapsed it will be hard to make an accurate comparison based on feel, since you wont' be able to clearly remember how he normally feels, especially if he is new to you so you don't know his "norm" very well. That may make it really hard to tell if he actually IS shortstriding, or if you are seeing what you expect to see.
If you THINK he will be sore and shortstriding, you will be predisposed to see this.
I had the same issue with my lease horse. I thought he was off but could not trust my judgement on this and had to have someone who knows his "norm" ride him to verify that, yes, he was shortstriding.