Firstly I am so sorry you are in this awful situation. It’s unbearable.
I mean this kindly, I really do: if I were you I would keep your money in your pocket.
Sending secret gifts for the past two years is more than enough evidence of a totally inappropriate ongoing relationship between your husband and another woman.
Deleting their conversation despite knowing you would want to see it, is more than enough evidence of a totally inappropriate relationship between your husband and another woman. Nobody needs to hide or delete normal conversations.
If a private detective caught him meeting her, you would just have one more very expensive piece of evidence that your husband is having a totally inappropriate relationship with another woman.
Nobody wants to believe it when they find out, OP, nobody. Or we don’t want it to be as bad as it is, or we want to find a believable excuse for it. It’s normal to feel that way.
However, it would still be just as hard to get your head round it as it already is, even if a private detective told you they’d met up.
If you need that for closure then I understand, and I certainly don’t blame or judge you for doubting anything and everything, I know I did.
Just be kind to yourself and set boundaries around what is and isn’t ok for you. And stick to them. He either complies with what you want or your relationship is over. You might decide you know enough for it to be over anyway, and that’s OK too.
I just don’t think money spent on a private detective is going to tell you anything that deep down you don’t already know. The important thing isn’t finding out more of the same stuff, it’s what you decide to do now. Sending virtual support your way OP. X