You really cannot rely on the bags turning up on Monday. And from all my years on FT I cannot recall a single example where intervention by passenger or staff would speed up delivery. It's like it is in the mail - it will be batch processed in due course. I see no point in trying to lobby for some sort of expedited service, it's just not feasible. There is a high chance that it will come through on Monday, 3 or 4 days is a fairly typical turn on delayed baggage. So you will need to think about approaching a chemist / pharmacy in where-ever it is you are in to get a replacement. Now if you have travel insurance with health assistance they may well have a helpdesk with clinicians able to do things like prescriptions or have local contacts who can help. I can't think of any major prescription items that is not widely available globally these days. Indeed if you are prescribed drugs from the NHS then almost certainly it will be on the European list, to give one example, and the UK's prescription rules are tighter than almost anywhere else, Australia is the only notable exception. So I think you probably would be able to get your medicine elsewhere. So many NHS drugs are freely available in overseas pharmacies. But at this point I'd hope you have Europ Assistance or similar.