I work in a nursery, I wouldn’t worry, the room usually has loads of other staff members who will ask, plus when they see the other kids go they all want to go haha. If you concerned just tell them he needs reminding and encouraging to go. I’m sure they will. When he starts he could have a few accidents but this will be due to the transition of a new environment. But in my place we encourage them to go ask regular. If you feel like they didn’t do this tho I’d speak to a manager, if no different take him out. Goodluck!
let them know the full routine with your little one, as he’s newly toilet trained say they need to prompt him to go and maybe bring up the idea of a toilet chart just so you have an idea of what’s going on. if they know the routine and that you want full transparency on what’s happening when he’s there they should accommodate xx