When I was going through promotion I was observed several times at a particular complex where there are two artificial pitches. One observer, who was also in charge of the promotion scheme, would always ask "why shouldn't this game have been played". The answer was no corner flags (as no holes to put them in), and that was all he was looking for and it was never mentioned on the report.
Thousands of games have been played on artificial pitches with no corner flags, just get on with it. On a grass pitch be seen to try and get it sorted out, but lack of corner flags shouldn't see a game called off. There is zero player safety risk, the only risk is you may give a goal kick instead of a corner or vice versa.