Harrison, who won 10 world titles at featherweight before a six-and-a-half-year absence from the sport, most of which was spent in a Spanish jail, was underwhelmed after the six-round contest against Joe Elfidh.
Harrison put his 32-year-old Nottinghamshire opponent down in the first round but lacked a spark in the rest of the contest, not showing the speed and determination to finish the job that marked his first comeback fight.
The 35-year-old later revealed he was desperate for another crack at a world title after being given hope by Warren that he could challenge for the WBO lightweight belt that fellow Scot Ricky Burns retained against Kevin Mitchell in the same ring at the SECC.
Harrison, who won every round, said: "I just treated it like a workout. Six rounds, I haven't done six rounds since I was 20 years old. I'm used to title fights. That was just like a spar.
"I will keep myself in the gym and hopefully get a world title fight.
"I left at the top, I never lost. I'm ready. I'll keep myself in the gym and I'll be ready in November.
"Frank Warren said I would be fighting November but I'll need to see what happens.
"Hopefully I'll be fighting for the title in November but I'll wait and see."
However, Warren wants Harrison to get more ring action before he will consider pitting him against Burns, who is due to fight again in December.
"Scott got messed around this week, I think that was his fourth opponent," Warren said.
"But he got rounds and that's what he needs. He needs to get as many as he can.
"The more rounds he gets, hopefully the better he will become. Him against Ricky would be a monster fight. If he gets some more wins, that fight could definitely happen.
"Everybody wants everything straight away, that's human nature, but it's not going to happen like that.
"He needs to box some more rounds, and that will be good for him."