this happened to me once with fortunately an experienced provider. In an intense cowgirl i did not notice the condom slipped off. Only after the fact did we notice. She was calm about it, I was mortified. She had really long nails and so she asked me to fish it out! I stuck my middle finger in her (true story) and could not feel the condom. I told her i can't find it. She calmly said ''keep looking hun''. I finally felt it at the very tip of my finger and somehow managed to get it out, 'phew'. Neeedless to say I became a regular of hers for a year and a half.
this has not much to do with the OP, but accidents happen and the consequences are usually none. But yeah you have to get tested.