I did see mile markers for miles 1, 2 & 3, but wasn't looking hard for them as I had my Garmin. The mile markers I did see matched my Garmin almost spot on.
I would hope the organisers make sure there is an explanation & apology; openness about the issues is always best at these times. Any excuses will only make people more annoyed & less likely to return.
I have to say I was surprised that the fun run started at the same time. However, I am relieved to see photographic evidence that the person dressed as a banana who overtook me was only doing the fun run.