I don’t think it’s right to say the OP shouldn’t have travelled - in today’s society, organisations have to accommodate customers with specific needs.

I think WTP is difficult due to lack of dedicated washroom. This does sound as though it wasn’t handled well and you were put into a situation where, despite trying to pre-plan, and receiving reassurances, your needs were not met. I am surprised as the lanyard is supposed to be well recognised, and cabin crew are very used to dealing with lots of people, all of whom will have specific needs.

Going forward, it sounds as though you should pre board and let the crew know that you need immediate access to a WC and agree with them that either you just come forward and use CW or F facilities as available or you’re to use the WT ones but the crew in that cabin will keep an eye out for you.

If a WW route there should have been a senior crew member (CSL) working in WT and regardless there should also be a specific crew member on each flight with the responsibility of looking after customers who have special assistance requests in their bookings, so it just sounds as though the crew didn’t realise who you were or register the seriousness of the situation. Again, I hesitate to make this your issue as you have done nothing wrong - going forward, I think making sure you pre board and that you do have that chat in advance and agree the plan would avoid a repeat.

Edit to add: in terms of having that conversation, you may be comfortable in simply raising it, but, if not, have you considered setting out on a side of A4 a bullet point list of what you need? You could then hand this to the crew at the door when pre-boarding. That way, you minimise how much you have to say in public and also can take time in advance to be specific so that there is no ‘lost in translation’ etc. IE:

- I have a medical condition which means I need to use the washroom regularly and without delay.
- I have on a previous flight experienced an incident where there was a large queue for the WT washroom and I was twice denied access to the Club washroom, resulting in me not getting to a washroom in time.
- I would like to agree with you, as operating crew, a plan to avoid and manage this for today’s flight to maintain the dignity of everybody concerned.

Don’t let this one incident prevent you from travelling.