The question remains, where are Thamud's vestiges?
It might be at the exact same place or different. For ancient civilization in desert, they shall revolve around source of water. And if the source of water still exist, the location may still attract inhabitants even millenias later.
This is the 2000 b.c civilization rock carving in egypt.

For Thamud's carving on mountains being 1000 years older than egypt one, the carvings may have withered much
But Al-Hijr is not in Egypt and water was still there in Al-Hijr.
Narrated 'Abdullah bin 'Umar (ra):
I bartered my property in Khaibar to 'Uthman (chief of the faithful believers) for his property in Al-Wadi(Qura). When we finished the deal, I left immediately and got out of his house lest he should cancel the deal, for the tradition was that they buyer and the seller had the option of canceling the bargain unless they separated. When out deal was completed, I came to know that I have been unfair to 'Uthman,
for by selling him my land I caused him to be in a land of Thamud, at a distance of three days journey from Al-Madina, while he made me neared to Al-Madina, at a distance of three days journey from my former land.
Imam Ahmad recorded that Ibn `Umar said, "
When the Messenger of Allah went to the area of Al-Hijr in Tabuk with the people, he camped near the homes of Thamud, in Al-Hijr and the people brought water from the wells that Thamud used before.