We have seen something similar. It's likely that you were re-exposed. That stuff gets everywhere and persists - rewash *everything* with Technu or your cleaner of choice - shoelaces are killer vectors for instance! That's likely what triggered the relapse, but the areas where we have previously had rashes seem to get exhibit a memory effect and will become inflamed a bit even if the exposure is on a different part of the body.
For example, the crook of my right elbow might show some mild inflammation even if the exposure was on my other hand! We have seen this repeatedly with both my wife and myself.
We have developed a protocol of Ivy Block (pre-exposure) /technu (wash tools, hands, arms)/zanfel (in a shower)for any time we have been exposed or will be working in a dangerous area. Also we keep our hicking shoes separate and ALWAYS wash our hands with techno after lacing or touching the boots.