"A clinical incident"

My partner was admitted at 12 0 clock midday on the 09/08/2016 for a hernia operation.When I phoned the hospital at 9.15 they could not find which ward he was in or if he had his operation. He was not checked by a nurse when he eventually returned from theatre in pain and had not not eaten for 26 hours.He was fitted with a drain after his op and notified the nurse this morning that there was no fluid in the bottle.My partner has just phoned me to say the drain came out of his tummy and lots of blood came out,they had left the clamp on the drain so it was not emptying at all.How could this have happened especially as he had pointed this out to them.