However, it's never too late to send a thank you - even two years later. This is less an etiquette question than a fashion one. The only time etiquette fashion plays in wardrobe is if your apparel is inappropriate for the situation. White shoes in December are probably out of place - unless you're in Arizona. Wearing white to a wedding is probably inappropriate - unless the bride asks you to.
Common sense applies here.
This question is too complicated to have a pat answer. If it's a co-worker, the supervisor really should be involved. If it's a loved one or family member, make sure that there is trust in the relationship before approaching them in a gracious way. This will certainly set them on edge. Be loving and gentle and understanding in your approach.