I am curious - What was the travel pass you had,and who withdrew it from you and why?
Regarding platelet donations;
1.Platelet donations have become much more important over the last decade. Used to support treatments of leukaemia or cancer for example, and can become very important in major trauma surgery to replace those lost through extensive bleeding.
2. The process of platelet donation is plasmapheresis, which requires fairly specialised equipment - can not be used in a mobile collection system.
3. The process of plasmapheresis is a process that is different from a standard blood donation and requires more supervision and support - another reason why it is not appropriate in an mobile clinic environment,
Only other thing I can think of is to see if any kind soul living locally to you would be willing to drive you in and back - maximum number of platelet donations annually would be around 6 times per year, if memory serves.