I worked for company P over the summer as an internship. A big part of working at P was doing a project for a customer, company Q. The project was exclusively ran by the interns at P, with a small oversight from upper management. The final part of this was a demonstration with two contacts from company Q. The demonstration was a success, and after exchanging information, we parted ways.
Recently I noticed that company Q is coming to my university for a career fair. Company Q is also looking for people with my major. Company P will also be at the career fair, though I do not know how relevant this is. Company Q is a company of over 100,000 employees, however, the location that they're very likely sending employees from has 200 or less.
Is it professional to cold-email two of P's previous customers, people whom I've only met twice, to find out more about why they're attending the career fair, and who i can contact further?
if this is acceptable, how do I contact the customer in a professional, yet brief manner?