something is eating my phal petals.....What could it be?
 

have not seen any evidence of insects and my 3 others that are in bloom are not being munched on. What could it be?

Did it open this way? The dorsal sepal covers the entire top portion of the bud and this may have been damaged prior to opening. Other suspects would be a slug or a curious cat if it occurred after opening.

no

That leaves an errant slug or physical damage.

Cut worms cause this type of damage. Small inch type worms can hide right in plain sight. Look closely along the stems of the plant. They blend in very well.

Try some beer traps to see if slugs are the culprit.

Also try leaving small slices of potatoes to see if there are any grubs that get on it.

Look at night. These are most likely nocturnal creatures. Don't look during the day.

I'll do that thanks