The town was designated as "no-entry" zone until August 10, 2012. The area where this tiny piece, with surface contamination of more than 100,000 cpm (meaning their survey meter went overscale), according to TEPCO, was found is currently designated as "Area preparing for the lifting of the evacuation order" (i.e. residents can return).
The 3 x 1.5 x 0.5 centimeter piece was found during the decontamination work being carried out by the national government.
Again, true to form for TEPCO/national government, the piece was found on June 20. The Ministry of the Environment asked TEPCO to analyze the piece on June 21. The piece was brought to Fukushima I Nuclear Power Plant for analysis on July 1. Announcement of the finding was on July 2.
I suppose TEPCO was trying to find a suitable container to carry the piece, for 10 days.
From TEPCO's Photos and Videos, 7/2/2013:
(Click to enlarge)
TEPCO's document above says:
The piece was found on the riverbed of Ide River in Naraha-machi at the river mouth, by the Ministry of the Environment on June 20. The decontamination crew was conducting the survey of radiation levels prior to decontamination, and found a hot spot on the riverbed, and collected this piece.
Surface radiation levels:
Gamma: 105 microsieverts/hour
Beta and gamma: 3,400 microsieverts/hour
Radiation levels at 30 centimeters:
gamma: 23 microsieverts/hour
Beta and gamma: 26 microsieverts/hour
Surface contamination: exceeding 100,000 cpm
The river mouth of Ide River is about 15 kilometers from Fukushima I Nuclear Power Plant.
Devastation in Naraha-machi, to the Ide River river mouth, video taken on the day the "no-entry" zone designation was lifted on August 10, 2012: