Ways not to lock your bike

My girlfriend just texted me to say she managed to lock her bike to someone else's for most of the day while she was in the library. Luckily he was nice about it, rather than being angry, or using the forum's suggested method of demanding she sleep with him.

a girl did this to me about a month ago. i was stressed and had plans for the evening and my bike was locked to someone else's! it was very inconvenient timing but i was an absolute gent. i just put my lock around both frames and left a note with my mobile number and an explanation. when i met her i made sure she understood how thoughtless it was in a nonaggressive way. i'm still proud of my lack of rant.

this makes me inexplicably angry