SorrelHorse, hope you don't tire of my likes; I just agree with you so often - LOL!
OP, the groundwork is what I was going to say, as well. Establish leadership on the ground first. I recommend Parelli 7 Games; it's all groundwork that builds the relationship & that transfers to saddle.
The BO has been negligent with you, imo. Hopefully you now see that at your savvy level, you were put into a risky situation by the invitation to "go ahead & ride", unsupervised at that. Savvy horsemen who've worked/ridden thousands of horses never just get on the horse, but rather do some groundwork to see what's up with the horse that day.