Lakshmana did not tell the name of Ravana while introducing themselves and their situation to Hanuman and Lakshmana told the following to Hanuman
"He who aspires to keep up the well-being of all the beings, and he who is merited for all comforts and respectability is now devoid of his prosperity and predisposed to forest dwelling... such as he is, his wife is abducted by a guise changing demon in a lonely place, of whom we know not... we know not which demon stole his wife... [4-4-13, 14]
But later Hanuman told to Sugreeva that Ravana stole Sita
"Ravana stole the wife of this principled one and great soul Rama when dwelling in forests, such as he is, he came seeking your refuge... [4-5-6]
How did the Hanuman come to know that Ravana stole Sita when Lakshmana explicitly told that they don't know who abducted Sita?