Argentine star Messi had just played a part in creating Barcelona’s late winner as his cross found Neymar, whose header was saved before Busquets lashed home the rebound to seal a 1-0 win in the 94th minute.
Barca players enthusiastically reacted to the match-winning strike and soon jumped on the goalscorer near the corner flag after he had slid to the ground in celebration, at which point Messi was hit by the object thrown from a section of the home support.
As the away players began heading back to the centre circle following the goal, Messi was still down on the ground clutching and rubbing his head. He was helped up to his feet by Rafinha, at which point he picked up the bottle with which he had been struck and threw it off the pitch.
The 27-year-old then rushed to the referee and protested while holding his head, only to be shown a yellow card with the official believing he was trying to waste time.
The final whistle blew just seconds after the re-start and Messi hugged a few of his team-mates despite being visibly irritated by the incident. He then stopped to receive treatment from the onrushing physio, with a cut already evident on his forehead.
The attacker continued to rub his head and returned to the referee in a second attempt to explain what had taken place before he left the field of play holding a tissue to the spot of his injury, giving the home support an ironic thumbs-up signal as he entered the tunnel.