Possible Clues:

• Person joining party, we hear, indulged in speculation
• Made an estimate
• Fancied lodger? Sounds like it
• Fancied one invited to the party, we hear
• Hazarded
• Conjectured correctly
• So-called visitor was a speculator
• Fancied one at the party, we hear
• Assumed one's invited for speech
• How one may have arrived at the answer that the one that's arrived is staying, by the sound of it