If they saw tendon damage on an US, it was likely there at that point. Tendon damage is graded on severity when ultrasounded, this one may have been minor at the time. Experienced race trainers can find things like this, the slightest change in a tendon that many people who are not as experienced may miss, and when they do, they get it ultrasounded. For the purpose of racing, even minor tendon damage when fresh is a career ending situation, because if the horse races like that, it will probably get worse, or much worse, or become terminal. Whether they decide to keep and rehab the bow themselves and hope to return the horse to the races, or whether to sell or “rehome” the horse to a different career depends on how talented a racehorse the horse has been so far in it’s race career. A “slight” bowed tendon is like being “a little bit pregnant” in race training and racing. It will heal, usually very well, if the horse does not race on it when fresh. It sounds like this is what has happened already. Yes, if small/slight tendon damage only, they can disappear from view entirely. If you want to US again, you could do that. Or, just start rehabbing the horse on the healed tendon, walking and trotting, prefer in a straight line (mounted), which is basically your regular light training that you would be doing with your new OTTB riding horse prospect anyway. Do NOT keep the horse in a stall for too long, light exercise is the key to rehabbing tendons. With a minor bow like this one, I would not keep the horse in a stall at all… stall rest for tendons is only for severe cases. Use some ace for the first day of turn out, to keep celebrations to a minimum. Then don’t lock the horse into a stall again. It is often the moment of turn out and the celebration that happens right after that, which is the dangerous part of allowing a healed or partially healed horse it’s freedom in a paddock.