Are you saying that when you decide to have a punt, there is always only ever ONE WG on that particular day, that floats your boat 
No, I'm saying that trying to arrange another SP at short notice is a pain in the arse and often results in disappointment and a waste of money, so I've found that it's better to just take the failure on the chin, don't stress about it or finding another SP and just go home maybe picking up a takeaway on the way and relax. Save your money for an SP you really want to see rather than one who was just available at the time. You'll enjoy it much more.
The alternative is madly searching for a suitable replacement, trying to get through to them and seeing if they're available and if they are then you may have to rush to them and then you might turn up late because your original plan involved you parking somewhere else and there's no parking near the new one and so you have stress finding car parking and the bastard car park requires you to use a fucking app that you don't have on your phone or you left your normal phone at home, so you get more stress to book the car park and then you have to eush to the new SP's venue and then she turns out not to look like her photos and she's pissed off because you srrived 10 minutes late because of traffic, getting lost, finding parking, downloading the fucking parking app, paying for the car parking and getting to her in an unplanned location. You start the booking with her pissed off and you stressed, so you can't get it up, but you've paid her so you spend 60 minutes not being able to have sex and then go home thinking that was a total disaster and you contemplate taking up woodworking instead.
Much better to not stress, get a takeaway, go home and relax knowing that you saved yourself some money to use to see someone you really want to see.