The bowl of the stone font was spotted missing from the mysterious Caynton Caves by followers of history fan Daniel Haigney's YouTube channel and confirmed when he paid a visit to the woodland site near Shifnal.
One of the rumours about the site it that it was an occult sanctuary of the legendary Knights Templar or another unknown religious sect. Daniel, from Shrewsbury, has not been able to find a reliable historic source to say what the caves were used for.
"It is a really special place," said Daniel whose YouTube Channel is called Third Rate content. "The font should be left in situ at the site.
"We don't know whether it has been stolen or taken away by the authorities, but we would love to see it returned to its rightful place."
Daniel, who records videos about interesting places across Shropshire, added: "A follower told me the the font is no longer there.
"I was really sad when I confirmed that to be the case. It has been there a long time and is a big part of the caves.
"It would have taken at least two people to get it out and the caves are not easy to get out of. There is a man-sized 'badger hole' that three people would not have been able to negotiate. It is also some distance from the road."
Daniel added: "If anyone knows where it is, I would love to know. People can let me know on the YouTube Channel."
In 2017 the Shropshire Star reported that a historian with knowledge of the Knights Templar claimed the dark caves were built by knights, making them several hundred years old.
Gretchen Cornwall wrote an account of the order’s survival to present day, called The Secret Dossier of a Knight Templar of the Sangreal.
Following new photographs of the cave by photographer Michael Scott, she has said the caves were genuine and were probably visited by a head of the order, who was executed in 1314. Previously it had been claimed that the caves may have been built by a wealthy family in the 19th century.
But Ms Cornwall said: “There is almost no information available to the public regarding the Caynton Templar Church as it has been erroneously labelled as a recent folly.
“The head of the Order, Jacques de Molay was executed on March 18, 1314. As the Grand Master of the Knights Templar it was his duty to visit the major preceptories of the Order. He visited Garway just to the south in 1294 and would have secretly visited the Caynton Templar Church as well.”
The Caynton Caves, hidden in dense woodland near Shifnal, were apparently carved out of sandstone.
Mr Scott, from Birmingham, set out in search of the historical wonder after seeing a video of it online.
Some of the sandstone chambers are so tiny that those exploring have to enter them on hands and knees.
The Knights Templar were a wealthy order of knights created in 1129 by the Pope who wore distinctive white mantles with a red cross over their armour.
Its original purpose was to protect pilgrims from bandits on their journey to Jerusalem.
It is said that the hand-made caves in Shropshire were used as a secret place of worship.
The Templars built their churches with circular naves, in imitation of the circular Church of the Holy Sepulchre in Jerusalem.