how difficult to say a thanks?

aRGH!!!!!!!!!!!!!!
I just couldn't imagine how ignorant and rude a person can be..
I woke up in the morning and before i forgot i went to my phone, text a message just to say "Have a Safe Journey" then i sent it.
But Even a single thanks that i get until now..
No Reply.
Can A person be VERY BUSY just to text and reply "thank you?"

not that i need the thanks so much, but don;t you think it is a ridiculous?
I Feel like a total douchebag right now..
why?
it seems like i concern too much about them..
i think i'll have to stop caring and minding other people's business..