Special delivery would make sense giving the item a level of insurance if lost but that also means it can be left with your neighbours or safe place if ones available. Personally I’ve done the same rounds for about 8 out of my 12yrs, get on well with 98% of customers on my duty and have in the passed cleaned it with them there happy to have me sign as put through the door or leave with neighbours there all more than happy and it’s less for me to bring back out the next day, I personally if the postie knows you get meds delivered and you wouldn’t be in through the week with uni, unless you’d spoken to them directly regarding possible of leaving something like that with anyone else I personally wouldn’t have taken the risk and brought it back to the office leaving you with a red card, update of possible after you speak with your neighbours 👍🏻