The Grecians missed a string of fantastic chances throughout the 90 minutes and were eventually made to pay when Joe Lennox's long-range effort cancelled out Liam Sercombe's opener to earn the struggling Pilgrims a point.
And Coles could not hide his disappointment at City's failure to beat their biggest rivals at St James Park.
"We were robbed really weren't we?" he told Press Association Sport. "It was two points dropped.
"We did more than enough to win the game and they didn't have a sniff, Artur (Krysiak) barely had a save to make, and they had a fluke of a goal that went in and that is very disappointing.
"We were well in control at half-time, and with any team winning 1-0 the emphasis was on the other team to throw everything at you.
"I don't think they really had any clear-cut opportunities and we had three or four and it should have comfortably been 4-1 or 5-1 really. It was disappointing all round to come away with just a point."
Thoughts now turn to another Devon derby on Saturday when Paul Tisdale's men travel to Plainmoor to take on a Torquay side who have lost just once there this season.
"Every game we play in seems to be so competitive in this league, whether a derby or not," Coles said. "But the derby on Saturday had a bit of extra spice to it which was nice and both sets of supporters were well behaved.
"I am looking forward to next week and going down to Torquay now."
- Sports & Recreation