My DH has a 'work wife' who he works with about 3 days a week... They get on well, they yell at each other sometimes, and also have some giggles. She rants at him on FB about how frustrated she is, and classes him as a good friend, who she trusts, and she hugs him occasionally (like when he has done her a big favour at work.) She is a single mom - 2 kids aged 14-16ish.
But she is also my friend, and talks to me quite a lot, and sends me a card, and a gift for my birthday, and also for Christmas... And DH and our kids too (and we buy for her and her kids!)
She goes to her country of origin (left there 20 years ago) every year, and brings us all goodies back. She tells people she thinks of me as a sister, and DH as a brother.
I am often invited to the works nights out, and she always sits near me and DH, and is very friendly, and a really nice woman.
I think if your husband's 'work wife' doesn't know you (or want anything to do with you,) that is a worry, but my husband's 'work wife' is as friendly with me as she is with him - so I am not bothered or worried.
Other women have a right to be worried of course; everyone is different. 
The situation in the OP sounds like it WAS a bit suspect. If you have no proof @issame if your DH is still up to anything, then try not to worry. Do keep an eye on things though.
Hope you're OK. 