I don't think we saw them, but Eileen spoke of showing Nicola some photos of her mum and Pat. It was when Nicola knew Pat could be her biological father and didn't want anything to do with him. Eileen thought showing Nicola some photos would help, as it would show it wasn't a 'dirty affair' and that they were in love. It backfired as Isaac, the man Nicola was brought up by, was in the background of one of the photos.
Doesn't necessarily mean he didn't rape her though - if Pat started as a friend of both as he claimed, they could have attended a party or something and Annabel could have danced with Pat as a friend as he was on his own. If Pat did rape her, perhaps the penny drops for Nicola when she asks to look again at the photos and realises they were all taken on the same night.
No doubt if he did rape her we can expect to see Pat claiming they were in love but Annabel must've told her friend he raped her as the friend realised they were having an affair.
It would be a good way of linking it all back to the Anna storyline, which could act as confirmation to Nicola. Some viewers will undoubtedly see that as rape as Anna didn't exactly consent freely.