We all have our own buying philosophies…here is what I would say about your story.
I guarantee that the horse you were looking at did not come up lame overnight. There was a history there that you were not told about.
You didn’t give details, but if this was an upper level horse, at that age and level of training, that horse probably had shown some signs of prior infirmities or weaknesses during training that were not disclosed to you.
This is why it is so important to VET THE SELLER. They live with the horse, know its mental and physical quirks and limitations.
There is no perfect horse, but getting young horses, you are not dealing with other people’s training. And horses that are in a “training for resale” program are sometimes pushed beyond the horse’s capabilities which can lead to mental and/or physical breakdown. I don’t want to deal with that, so I buy young.
I like training horses. I like to work with young horses. I have had European trainers say, “Have I got a horse for you.” In one case it as a GP stallion that had a price “only for me.” I passed…never went further than the conversation and a video of the horse.
I like to start with the blank chalkboard that is a young horse. Some are more athletic and/or more intelligent than others…but in all cases, they provide me with lessons in horsemanship that advance my equestrian tact.