Lost bright blue silicone Speedo swim cap with initials 'J.S.' left on the grass by the picnic area at Clapham Common.

I was swimming at Clapham Common on Sunday afternoon and I realized later that I left my bright blue swim cap behind on the grass by the picnic area. It's a large silicone one from Speedo, with my initials 'J.S.' written on the inside. If anyone finds it, I would appreciate getting it back as it's quite important for my training sessions!