Many are familiar with the prayer to St. Anthony to find a lost item, but there are numerous Anthonys in the list of Catholic saints.
For example, the "first" St. Anthony is arguably St. Anthony of Egypt, also known as St. Anthony the Great. He was a hermit in the 3rd century and his way of life inspired many others to follow in his footsteps. However, he is not typically called upon for his intercessory prayer to find a lost item.
Another possibility is St. Anthony Zaccaria, a priest in the 16th century who promoted Eucharistic adoration. He is not the St. Anthony we are searching for (or, who is known to be searching on our behalf!).
Which St. Anthony is the one who intercedes for you to find something that was lost?
The most famous St. Anthony in the Western world is St. Anthony of Padua, who is also known as St. Anthony of Lisbon (he was born in Lisbon, but died in Padua).
He is the one who most frequently intercedes for those who are searching for a lost item.
This is not to say that the other saints named Anthony won't intercede for you when you need to find something. They certainly will, but it is St. Anthony of Padua who is most frequently consulted in such a situation.
If you need to find something that was lost, pray this prayer to St. Anthony of Padua.
