Gamanit hit the nail on the head.
If I send a gift, hand it to a person at a simcha in charge of receiving the gifts, etc. I am not sure the intended recipient received it unless I receive a thank you card or other acknowledgement. I’m talking about a physical gift; not a check which clears the bank and appears on my statement.
If I have not rec’d a thank you card (or phone call, email, etc.)90 days after the simcha I contact the intended recipient and ask if the item was received or lost.
My children have been raised that a gift may not be used until a thank you note has been written, envelope addressed, stamped and placed in the outgoing mail.