I really think there is something to this. I don't have this exact experience with residual detergent but I do believe that soap contributes to outbreaks. Years ago, near the time of first getting this awful virus, I discovered that regular bar soap & even a baby wipe or other type of cleansing wipe would cause me to get an outbreak. So I stopped with the wipes all together & now I use a soap that it's only ingredient is olive oil. I learned that I had to use this soap on everything above my knees to below my belly button & it really has reduced my outbreaks! Also NO lotion above the knee!
Extra Rinse Your Underwear
I have found that putting my underwear through an extra rinse cycle, I haven't had an H2 outbreak for over a year. Previously I suffered for 2 years from monthly, bi-monthly and sometimes non stop out-breaks for months on end. I believe that the laundry detergent residue left on my underwear was the trigger for all of my outbreaks. I found that rinsing my underwear again got rid of the left over detergent and the cause of my outbreaks.