postage issue question

[the mad1]

i sold a rc car and posted it via standard parcel but the buyer says he hasnt received it so i then sent the post office and email they responded with an email saying they would get back to me asap this was about a week ago and i have not heard anything from them is this normal as i have never had this issue before
or should i get back onto them about it?
i tell you what though il never use royal mail again after this experience