Eh, reason why I generally don't like to read too deep into things.
Especially time travel.  Often opens up a can of worms.  I'm personally not a big fan of it being used in fiction.

I looked back at episode 3 when Mami is killed and some red string-like stuff seems to go through Homura's hands - but it doesn't really show any resemblance to a ribbon though.

Also the scene where Homura finds the ribbon seems to be one of the "middle timeline" scenes (when, originally, Kyoko is killed by Mami), but Homura doesn't have the glasses or tied hair in that situation.  One would've expected that the world would revert to a pre-Homura-time-travel state, rather than something in the middle.