After a lack of clear-cut chances in front of goal, the Magpies took the lead through Jonjo Shelvey's venomous free-kick before two second half penalties, both netted by Preston's Paul Gallagher, sealed the pre-season victory for the Lilywhites.
But Longstaff, who was partnered alongside Shelvey and Isaac Hayden for the opening 45 minutes at Deepdale, admitted his delight in featuring alongside the midfield pair as well as earning a first start for his boyhood club after progressing through the youth ranks at Newcastle's Academy.
The 19-year-old told nufc.co.uk: "I'm trying to soak everything in like a wet sponge. You don't get to do a lot of pre-season with the first team so now I have the chance to do it, I want to try and take everything in and become a better player and hopefully get to where the first-team players are at.
"I thought we were very good in the first half. I wasn't able to watch the second half as I was getting changed but Jonjo scored a good free kick and, overall, I enjoyed it.
"I can't thank the manager enough for giving me a chance. Every chance I get I will keep trying to take. At the minute, I just want to keep enjoying it and try to learn from all the pros to get better.
"Playing with Isaac and Jonjo was a massive help. Isaac spoke a lot to me on the pitch and Jonjo is one of the best passers in the Premier League. You don't get to play with many people like them that often so doing that was really great and I think they both helped me a lot."
Backed by 1,359 Newcastle fans, despite the heavy rain in Lancashire, Longstaff - raised in North Shields - heavily praised the following from his fellow United supporters.
The teenage midfielder thrived in unpleasant conditions, admitting the strong support was a positive factor during the friendly clash despite the narrow defeat against the Championship outfit.
He added: "It means a lot as a local lad, especially after hearing the fans singing. It's not surreal because obviously you want to do it for the first team but just hearing them today was great.
"I spoke to Sean (Longstaff) about it as he experienced it all last year. As a local lad growing up, you always dream of playing for Newcastle United and even doing it here (at Preston) has been really good.
"I thought the fans were excellent. It's weird because when I was running through they started singing and I thought 'they are very loud'. You were the one who used to be sitting in the stadiums singing or chanting yourself.
"That started to play through my mind a bit and I thought 'get back into the game here'. The fans are always amazing. Growing up, I was one of them and I loved it. They are some of the best fans in the world."
