I've seen this before. Did someone re-seal your Oil Pump at some time? Subaru uses grey sealer, not blue. If too much sealer is used on the Oil Pump it goes directly to the Filter and is trapped in the Filter intake (outer ring).
I would take pictures and get acknowledgement from the dealer that they saw it. If the dealer did the Oil Pump work you might want to talk to the SOA rep too. If there was only a few pieces of sealer in the Filter you don't have anything to worry about.