My apologies.
I concentrated on "Don" (which immediately precedes his name, and not Infante).
According to
Wikipedia:
"Rarely used, the Prince's style and title in full is: His Royal Highness the Most Serene Infante Don Felipe Juan Pablo Alfonso de Todos los Santos de Borbón y Grecia, Prince of Asturias, Prince of Girona, Prince of Viana, Duke of Montblanc, Count of Cervera and Lord of Balaguer."
At the same time,
the page dedicated to Prince Felipe's titles and styles does not mention "Infante" among them. According to that article, his official title is
"His Royal Highness Prince Felipe Juan Pablo Alfonso de Todos los Santos, Prince of Asturias," Prince of Girona, Prince of Viana, Duke of Montblanc, Count of Cervera and Lord ofBalaguer." It's not the full official title though, so I'd assume Infante is still somewhere there.
I checked the official website of the Spanish Royal Family (in English and Spanish) but there is pretty much no information on Felipe's titles bar the shortest official version. I still don't see why he would lose the title of Infante though.
Again, according to
Wikipedia:
Interestingly though,
the Spanish version of the article directly contradicts the English version and states that the title "Infante" is reserved for the children of the Monarch and the heir apparent (but
not the heir apparent himself who enjoys the higher title of a Prince - Prince of Asturias), and others whom the King will see fit to invest with the title. According to the Spanish version, the only Infante right now is Carlos of the Two Sicilies, Duke of Calabria.
Go figure!