I have found it more or less ... and there was a reason why this "source" was deleted .. It was because it was a journalist who was supposedly citing a PAF official ...not on a published article .. but his twitter ... and the tweet was posted on here by an Indian friend who created an entire thread on it ... if Im not mistaken ...
In the events that followed, He was called out by defence.pk .. to which his response was that he talked to a paf official .. regarding this news ...
Unsurprisingly ... no further comments ever came from his side after the Janes published a piece in which they cited a PAF official saying that talks were on for SU-35 ...
So its the credibility of a journalist whom we've never even heard from ... versus the credibility of Janes ... one of the most reputed and credible source of information in the defense industry ... you can take your pick ....
Lastly, regarding the series of events you posted ... they are quite off ...
1. Originally after the MMRCA, there were suggestions to the Russian administration, that they should try and sell the Mig-35 that India rejected to Pakistan ... (2011)
Russia Experts Says Russia Could Sell Mig-35 Fighter Jets To Pakistan - ASIAN DEFENCE NEWS
2.Rumors of Pakistan being interested in SU-35 have swirled around .... (2012)
Is PAF going to get 24 Su-35 fighter?
3. Sputnik international reported regarding the SU-35 and its exports in which Pakistan was reported as a potential customer .. (July, 2015) (Article by Ilya Kramnik)
Russian Su-35 Fighter Jet Sees Export Orders Soar
4.Sputnik International quotes Russia's deputy foreign minister, reporting that he said that they were in talks with the Pakistani counter parts regarding the delivery of Mi-35 and SU-35. (September 2015)
Russia-Pakistan Military Cooperation Not Threatening Relations With India
5. This is when the whole commotion starts, with different blogs, websites etc. posting their take on the development, this also happens to be the time frame when that tweet from that journalist came along and a similar tweet from an Indian journalist came along who was claiming that Russian embassy has rejected such reports ... You can find it all on google as quoting all of those sources will take alot of time... but this is the crux of what happened after the news broke ...
6. The only official word that is actually reported that was supposedly against this news was reported by many Indian based websites ... yet I have not found sites with the repute of Janes or sputnik reporting it ... however even in the report itself there is no solid negation of the whole deal as it only says that Russia won't take any step detrimental to India's security ... (September 2015)
Will not take any step detrimental to India's security: Russia | Zee News
7. The confirmation of the talks from the Pakistani side came along when Janes confirmed it ..
Pakistani official confirms Su-35 talks - IHS Jane's 360