Ok, in a very desperate way to find my SID since I don't have access to either Wi-FI or an AR, I tried something with Pandora's box.
I remember on what day/date I started my HG game so in the Seed Finder part of Pandora's box I put my trainer ID (64441), month : 4, day : 29, year : 2010, and I covered three hours : 17/18/19 since I can't remember perfectly which one it was but I'm 100% sure it was one of these three. As for the delay, I've covered a very large branch and put 5000 min 10000 max.
I tried different minutes to get different seed/delay/SID combinations, I noticed that they come back multiple times so in the end you get only ~5/6 SIDs for one hour with my input. (I only took even delays in the lists since that's what I always get)
So in the end I had ~15 SIDs to check, and in order to do this I've searched in the Time Finder of RNGReporter for seeds with a shiny on frame 2 with my ID trainer and one of the SIDs I had to check, then hit the seed to catch the pokemon on frame 2.
I repeated this process for each SID I had, and none on the pokemon I found were shiny, soooo how could this be ?
Did I misunderstand something about pandora's box ?
I am 100% sure my infos are correct, and that I hit the correct seeds (the pokemon had the correct nature and ivs but weren't shiny).
Sorry if this all was unclear I tried to explain what I did very deeply but well.. if anyone wants to help feel free to ask me precisions..
Thanks