The animal welfare charity received a call saying there was an injured or possibly dead snake at Green Street Park.
It said the caller had been "too scared" to get any closer.
SSPCA animal rescue officer Coreen Hill said it was "always better to be safe than sorry."
She said: "I expected to be met with an escaped corn snake that had been attacked by a cat or dog, but instead I discovered it was made of plastic.
"The caller believed they had spotted a snake in the distance whilst at the park and was too scared to get any closer to investigate.
"They could only tell that it wasn't moving and had its mouth open.
"This job can be very tough as we deal with severely injured animals on a daily basis, so it's quite nice when something like this makes us smile."

Both blasts went off on Thika road, a busy highway north-east of the city.
The buses were crowded at the time of the explosions, which police said were caused by improvised devices.
Sunday's attack was the second in Kenya in as many days. Recent violence has been blamed by the government on Somali Islamist group al-Shabab.
According to reports, the two explosions went off outside a hotel and at an underpass not far from Kasarani, north-east of the capital.
Kenya's National Disaster Operations Centre said 20 of those wounded were in a critical condition.
The buses were badly damaged by the explosions. Television footage showed a gaping hole in one, while the doors and windows were blown out of the other.
On Saturday, a grenade was thrown in a bus in the coastal city of Mombasa leaving four people dead and another 15 wounded. The bus had just travelled from Nairobi. There was a second blast near a beach-front hotel, but no-one was hurt.
The al-Qaeda-linked group al-Shabab has launched a series of attacks against Kenyan targets in recent years in retaliation for Kenya's military involvement in Somalia since 2011.
In September, at least 67 people were killed when al-Shabab fighters seized the upmarket Westgate shopping mall in Nairobi for four days.
Kenya has vowed to halt attacks by militant Islamists and arrested some 2,000 people in the capital last month.

It shed 2.4%, or 118 points, to close at 4,876 as semiconductor and biotech stocks fell sharply.
The decline was the Nasdaq's biggest one-day fall since April 10 last year.
It came despite shares in Kraft Foods, which is listed on Nasdaq, soaring more than 35% after the company agreed to merge with Heinz.
The merger between the ketchup maker and the company that owns brands including Philadelphia cream cheese is set to create the third-largest food group in the US.
Microchip maker AMD fell 5.7% following a broker downgrade, while Oramed Pharmaceuticals was the biggest faller, off 19%.
The Dow Jones lost 292 points, or 1.6%, to 17,718, while the S&P 500 dropped 30 points, or 1.5%, ending at 2,076.
On the currency markets, the dollar fell 0.5% against the euro, to â‚¬0.9114. The slide followed data showing US durable goods orders fell 1.4% in February - the third decline in four months.
"Today's report provides strong evidence that the manufacturing sector is feeling some considerable heat from the stronger dollar," said Anthony Karydakis, chief economic strategist at Miller Tabak in New York.
The Scottish SPCA was alerted by a member of the public to a snake in Forfar only to discover it was a plastic toy.
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Three people have been killed and at least 62 others wounded in two explosions on passenger buses in the Kenyan capital Nairobi, officials say.
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(Close): The main US share indexes all slumped on Wednesday, with the technology-focused Nasdaq sustaining the heaviest losses.