Well I am on my hobby horse, I was brought up (many moons ago) to always send a thank you card when having received a present, even if I have received it from that person. Nowadays this seems to have gone out of fashion, occasionaly I may receive a text message form one of my four Grandchidren, also I send a little cash electronically, to them, when they are doing something special, but rarely receive a thank you. I think if having sent money in a card, it is wise to ring and ask if they have recieved it, if they dont acknowledge it them selves, things can be mislaid in the post! This can be a gentle reminder, that it is manners to say thank you, in any way or form.
Stepping down from my hobby horse now.