弄丢了西瓜的夏天
[nòng diū le xī guā de xià tiān]
It implies a sense of loss or regret during the summer, as watermelon is typically enjoyed in summer. The netizen probably feels a certain disappointment or nostalgia about an experience they went through, which can be understood in terms of missing out on a pleasant moment. The lost 'watermelon' could symbolize any happy and sweet memory, love, or other precious things.