My 8yo just had this surgery. I am not happy that three doctors missed it, but guess that they could have ascended. Some studies suggest this is more common that previously thought. When it was finally caught our ped acted like I should have noticed. I haven't felt - nor closely examined - my kids scrotum since we was 2. But they have. Anyway.
The surgery went okay. I recently underwent surgery for a ruptured appendix and so I think that helped my son know what to anticipate. They told me twice over the phone that I would be with my son when they started anesthesia, when, in fact, that was not allowed. So check with that before you make your kid any promises. They will likely sedate him before anesthesia, but my son remembered everything and was scared and sad that I wasn't with him when they started anesthesia. We talked about it a lot beforehand, and with his 5yo brother. Anticipating questions was heklpful for him because he has a hard time articulating his big feelings. I would say "Are you wondering what happens with anesthesia" or "Are you worried about what it will feel like afterward?" He worried a lot about the fasting beforehand and the activity limitations afterward, so we had an elaborate plan for all of that.
Ask your surgeon what the testicle looks like. Because its jsut one, your son will likely be just fine. Testicles that are a healthy size and appearance have had good blood flow and are more likely to be normal. My son's were both inguinal with good blood flow - the surgeon said, somewhat insensitively "If I were a betting man I would guess you'll have grandchildren." Sigh.
Recovery was okay. My son was in a lot of pain for about 24 hours and hated the liquid pain medicine. Luckily he can swallow pills so he got half an adult dose of ibuprofen. Swelling made him bow-legged for about 4 days. We made the first two days post-p[ fun with lots of screen time, junky food, family movies and cuddles.
We are 3 weeks post-op and he went on his first bike ride yesterday. No pain or issues at all. Has been climbing trees since 10 days after surgury.