I am not sure why, at what point, or which bezodiazepine you were given. However, the doctors obviously gave you one and it caused a problem with you waking up from anaesthia. They probably do not know exactly what the problem is either.
However, to protect you in the future they told you to tell doctor's what happened so that they do no give you benzodiazepines because you may have a negative reaction. It should be in your doctor's notes about "drugs allergic to" but other than warning the doctor, you may never come across this problem again. Benzodiazepines are "controlled" substances like methodone and are usually used by psychiatrists to help the mental health of their patients.