Is that the only "proof" you have? Look, I smell affairs probably as often as anyone on this forum, but a lingerie receipt is not really proof. Certainly not the kind of iron-clad proof you want to hang your hat on.
It could easily be just your wife, wanting to feel more sexy and attractive just for HER (us guys always think it's all about us, but it's not!), or -- more likely, since you said she left it out where you could easily find it -- it COULD be a trap she laid for you. Certainly wouldn't be the first time I've seen that around here.
