Tomic looked shattered after a 6-1 6-7 (5-7) 6-4 defeat on Sunday, calling for the trainer and not moving to return serves in the often-punishing first set.
He rallied in the second set to force a decider but came up short, snapping his seven-year streak of playing in every major and leaving him at a career crossroads.
He was spent after the taxing loss, sarcastically responding to journalists asking him where he'd go from the loss.
"I just count money, that's all I do. I count my millions," he said.
"You go do what I did. Bye bye."
Tomic, the world No. 142, will further slump in the ATP rankings as he will lose his points earned from a third-round appearance at Melbourne Park last year. He misses his home Grand Slam for the first time since 2008.
Tomic's performances earlier in the week gave hope that a comeback could be on the cards for the fallen former Australian No. 1.
He routed Vincent Millot in 48 minutes and then steadied against American Tommy Paul in the second round, winning in a third set tiebreak.
But Tomic's final singles outing at Melbourne Park began as a no-contest.
He won just 11 points in the first set, looking nonplussed at the Italian's procession of winners.
Moving poorly and with no intensity, Tomic simply gave away points on Sonego's serve deemed out of reach.
It was a sorry sight, exacerbated by the scheduling of the 2011 Wimbledon quarter finalist and biggest name in the qualifying tournament, on court eight.
Out of nowhere, he lifted in the second set, maximising his effort in his own service games to push through.
At 6-5, the Tomic grunt was back.
The crowd lifted with the Queenslander and he responded in the second-set tiebreak, fist-pumping his way back to the chair as he levelled the match.
Lorenzo showed signs of agitation for the first time in the third set, shaping to throw his racquet as he grappled with Tomic's improved serve.
A rare break point for Tomic in the ninth game roused the crowd but the Italian responded with two sensational winners.
Lorenzo maintained his week-long streak of service holds, pushing the contest towards another another tiebreak.
At 5-4, Tomic double faulted to give away match points, pulling out a huge winner down the line to continue his resistance.
It couldn't last, with Sonego closing out the match and richly celebrating his first main draw appearance at a grand slam.
Whether Tomic returns to the tour in a full-time capacity is yet to be made clear.