If it's not occupied for an hour or so just remove it and take to front desk or towel exchange booth. I've done it before and works. If you don't feel comfortable get security or someone from management do it for you. If it's a resort policy they'll have to enforce it for you if you ask them to.
My guess is that some "tip" the workers around the pool area and therefore nothing is ever done. I know you stay at Flamingo but is has always been rampant at Royal Palm, both around the pool and on the beach. Security....yea, right.
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