The Argentine suffered a miserable night with his teammates as Jurgen Klopp’s men completed a stunning comeback to knock Barcelona out of the Champions League.
The Catalans appeared to have won a place in the final after a commanding 3-0 win in the first leg at Camp Nou last week.
But Liverpool scored four goals without reply to book their place in the Champions League final in Madrid on June 1.
Messi was required to undergo a doping test immediately after Barca’s crushing defeat at Anfield.
El Chiringuito reports that the process took so long that Barca’s team bus headed to the airport while Messi was still at Anfield.
The Argentina captain was eventually able to provide a urine sample, while special arrangements were made to reunite the Argentine with the rest of the squad and coaching staff before they travelled back to Spain.
Messi, who refused to address the press, also walked through the mixed zone at Anfield.